Rotating compact light ranging system

ABSTRACT

A light ranging system including a shaft; a first circuit board assembly that includes a stator assembly comprising a plurality of stator elements arranged about the shaft on a surface of the first circuit board assembly; a second circuit board assembly rotationally coupled to the shaft, wherein the second circuit board assembly includes a rotor assembly comprising a plurality of rotor elements arranged about the shaft on a surface of the second circuit board assembly such that the plurality of rotor elements are aligned with and spaced apart from the plurality of stator elements; a stator driver circuit disposed on either the second or the first circuit board assemblies and configured to provide a drive signal to the plurality of stator elements, thereby imparting an electromagnetic force on the plurality of rotor elements to drive a rotation of the second circuit board assembly about the shaft; and a light ranging device mechanically coupled to the second circuit board assembly such that the light ranging device rotates with the second circuit board assembly.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/596,018, entitled “Compact LIDAR System,” filed Dec.7, 2017, the disclosure of which is incorporated herein by reference inits entirety for all purposes.

This application is related to the following commonly assigned andconcurrently filed patent applications, the disclosures of each of whichare incorporated herein by reference in their entirety for all purposes:“Light Ranging System with Opposing Circuit Boards”, U.S. patentapplication Ser. No. 16/209,869 (Attorney Docket Number 103033-P010US2);“Rotating Light Ranging System with Optical Communication Uplink andDownlink Channels”, U.S. patent application Ser. No. 16/209,875(Attorney Docket Number 103033-P010US3); and “Light Ranging Device witha Multi-element Bulk Lens System”, U.S. patent application Ser. No.16/209,879 (Attorney Docket Number 103033-P010US4).

BACKGROUND

Light imaging, detection and ranging (LIDAR) systems measure distance toa target by illuminating the target with a pulsed laser light andmeasuring the reflected pulses with a sensor. Time-of-flightmeasurements can then be used to make a digital 3D-representation of thetarget. LIDAR systems can be used for a variety of applications where 3Ddepth images are useful including archaeology, geography, geology,forestry, mapping, construction, medical imaging and militaryapplications, among others. Autonomous vehicles can also use LIDAR forobstacle detection and avoidance as well as vehicle navigation.

Many currently available LIDAR sensors that provide coverage andresolution sufficient for obstacle detection and avoidance in autonomousvehicles are both technologically complex and costly to manufacture.Such sensors can thus be too expensive to allow for wide deployment inmass-market automobiles, trucks and other vehicles. Overall componentcost and manufacturing complexity of a particular type of LIDAR sensoris typically driven by the underlying complexities in the architectureof the LIDAR sensor itself. This can be further exacerbated in somemodern LIDAR sensors which are a conglomeration of different internalsub-systems, each of which can be in itself quite complex, e.g.,optoelectronic systems, electromechanical systems, computer controlsystems, high-speed communication systems, data processing systems, andthe like.

To achieve the high positional accuracy, long distance range, and lowpower consumption that can be important to some modern sensingapplications, stringent technical requirements for each one of thesesub-systems have led to architectures and designs that are complex anddifficult to build and often require expensive calibration and alignmentprocedures before individual LIDAR units can be used by a customer. Forexample, some LIDAR systems have internal architectures that employ oneor more large motherboards and bulky, heavy optical systems that aremounted on a counter-balanced structural member, all within a turretthat rotates at rates on the order of 1,000 RPM. In some of thesesystems, separate laser emitter/detector pairs are mounted toindividual, separate circuit boards. Thus, each emitter board andreceiver board can be required to be separately mounted to themotherboard, with each emitter/detector pair precisely aligned along aparticular direction to ensure that the field of view of each detectoroverlaps with the field of view of the detector's respective emitter. Asa result of the above architecture, precision alignment techniques aretypically required during assembly to align each emitter board and eachreceiver board separately.

The above-described architecture becomes increasingly problematic whenone desires to scale the resolution of the device. Increasing theresolution requires the addition of more laser emitter/detector pairs,again, each mounted on their own circuit board. Consequently, scalingthe resolution linearly with this type of architecture can lead toexponential increases in manufacturing costs and also exponentialreductions in reliability due to the sheer number of individual partsand boards involved. Once assembly and alignment is complete, great caremust be taken that the precisely aligned multi-board arrangement is notdisturbed or jolted out of alignment during shipping or at some otherpoint over the design life of the system.

In addition to the complexities of alignment and assembly of the opticalsystems, most currently available LIDAR units have a relatively lowoverall degree of system integration. For example, control and drivecircuits in many currently available LIDAR units are separate modulesmounted to custom boards. These custom boards may, in turn, need to bemounted to a motherboard within the LIDAR unit or may be mountedsomewhere else on a structural element of the LIDAR unit by way of oneor more mounting brackets. In some cases, each board can have one ormore electrical interconnects that need to be routed through one or moreinternal volumes or passages within the enclosure to eventually connectwith the motherboard.

For rotating LIDAR systems even more additional specialized mounts andinterconnects may be required for the electric motor rotor and/orstator. In addition to power connections, data uplink and downlink linesare needed and typically accomplished by one or more inductive,capacitive, and/or metal slip ring rotary couplers, which can bedifficult to implement and/or lead to low rates of data transfer. Somesystems employ metal brushes within the rotary coupler and are thuspotentially unreliable due to the requirement of mechanical contact ofthe brushes within the rotary mechanism. Other slip ring-type connectorscan employ hazardous substances, such as mercury, causing these types ofcouplers to be non-compliant under the Restriction of HazardousSubstances Directive 2002/95/EC (ROHS) and thus disfavored or evenbanned in some jurisdictions.

With respect to the optoelectronic systems, the industry has experiencedchallenges in incorporating cost-effective single photon photodetectorssuch as CMOS-based single photon avalanche diodes (SPADs) due to theirlow quantum efficiency in the near infrared wavelengths and their lowdynamic range. To improve quantum efficiency, some SPAD-based detectorsemploy InGaAs technology but such systems are more challenging tointegrate in a cost-effective manner than CMOS devices. Therefore, theexternal/supporting circuitry (e.g., a quenching circuit that can sensethe leading edge of the avalanche current, generate a standard outputpulse synchronous with the avalanche build-up, quench the avalanche bylowering the bias back down to the breakdown voltage, and then restorethe photodiode to the operative level) associated with the SPADdetectors manufactured using InGaAs technology is typically fabricatedseparately from the SPAD array, for example, in a package that isexternal to the SPAD array. In addition, InGaAs substrates arerelatively expensive and the associated manufacturing processestypically have a lower yield than silicon substrate manufacturingprocesses further compounding the costs increase. To complicate mattersfurther, InGaAs substrates typically need to be actively cooled in orderto reduce dark currents to suitable levels, which increases the amountof energy consumed during runtime, increasing cost and complexity evenfurther.

Rather than employing SPAD-based detectors, many commercially availableLIDAR solutions employ avalanche photodiodes (APDs). APDs are not binarydetection devices, but rather, output an analog signal (e.g., a current)that is proportional to the light intensity incident on the detector andhave high dynamic range as a result. However, APDs must be backed byseveral additional analog circuits including, for example, analogcircuits such as transimpedance amplifiers and/or differentialamplifiers, high-speed A/D converters, one or more digital signalprocessors (DSPs) and the like. Traditional APDs also require highreverse bias voltages not possible with standard CMOS processes. Withoutmature CMOS, it is difficult to integrate all this analog circuitry ontoa single chip with a compact form factor and multiple external circuitmodules located on a printed circuit board are usually employed whichcontributes to the high cost of these existing units.

Accordingly, to support growing markets for 3D sensing systems, thereremains a need for more cost effective but still high performing LIDARsystems. Furthermore, there remains a need for improved and more elegantsystem architectures that enable streamlined assembly processes that canbe effectively employed at scale.

SUMMARY

Embodiments of the disclosure pertain to a LIDAR unit that can, amongother uses, be used for obstacle detection and avoidance in autonomousvehicles. Various embodiments of the disclosure can address one or moreof the problems discussed above that are associated with some currentlyavailable LIDAR systems. Some specific embodiments pertain to LIDARsystems that include design features that enable the systems to bemanufactured cheaply enough and with sufficient reliability and to havea small enough footprint to be adopted for use in mass-marketautomobiles, trucks and other vehicles.

In some embodiments, a spinning light ranging system according to thepresent disclosure can include a light ranging device (e.g., which emitslight pulses and detects reflected pulses) that is connected to an uppercircuit board assembly that rotates about an axis defined by a shaft.The upper circuit board assembly can cooperate with a lower circuitboard assembly, e.g., to provide power, data, and/or encoded positions,via respective circuit elements. The inclusion of cooperating wirelesscircuit elements on the rotating upper board assembly and the lowerboard assembly (e.g., as opposed to external, physical connections) canprovide for a more compact design. Further, specific circuit elements(e.g., optical or power) can be positioned in a manner to enableefficient communication and/or to increase flux. For example, a wirelesspower receiver can be provided at a ring at an outer edge of the uppercircuit board assembly, maximizing the amount of magnetic flux capturedby an inductive ring or maximizing the area available in a capacitivesystem.

According to some embodiments, an optical communications subsystem canprovide an optical communications channel between a rotating lightranging device and a base subsystem that does not rotate about a shaft.The optical communications channel can provide for fast communications,but also can provide for a compact and inexpensive design. For instance,a turret optical communication component can be positioned on a rotatingassembly to communicate data (e.g., ranging data from the light rangingdevice) with a base optical communication component. Such positioningcan alleviate the need for more bulky communication mechanisms. Forexample, downlink transmitter can be positioned to transmit opticalranging data through a hollow shaft used for rotation. As anotherexample, one or more uplink transmitters of the base subsystem cantransmit uplink signals to one or more uplink receivers that rotate on arotating assembly, e.g., where these uplink elements are positioned inrings that align.

According to some embodiments, a rotation of an upper circuit boardassembly can be driven by stator and rotor elements integrated on upperand lower circuit boards, thereby making the light ranging systemcompact. For example, the upper circuit board assembly can include aplurality of rotor elements symmetrically arranged about a rotationshaft, and a lower circuit board assembly can include a plurality ofstator elements symmetrically arranged about the shaft. A driver circuitcan drive the stator elements. Having such rotor and stator elementsbuilt onto the circuit boards themselves provides various advantagesover products that use bulkier motors (e.g., stepper motors, brushedmotors or unintegrated brushless motors).

According to some embodiments, a light ranging system includes a shafthaving a longitudinal axis; a first circuit board assembly that includesa stator assembly comprising a plurality of stator elements arrangedabout the shaft on a surface of the first circuit board assembly; asecond circuit board assembly rotationally coupled to the shaft andspaced apart from and in an opposing relationship with the first circuitboard assembly, wherein the second circuit board assembly includes arotor assembly comprising a plurality of rotor elements arranged aboutthe shaft on a surface of the second circuit board assembly such thatthe plurality of rotor elements are aligned with and spaced apart fromthe plurality of stator elements; a stator driver circuit disposed oneither the second or the first circuit board assemblies and configuredto provide a drive signal to the plurality of stator elements, therebyimparting an electromagnetic force on the plurality of rotor elements todrive a rotation of the second circuit board assembly about thelongitudinal axis of the shaft; and a light ranging device mechanicallycoupled to the second circuit board assembly such that the light rangingdevice rotates with the second circuit board assembly.

In some embodiments a light ranging system includes a shaft; a firstcircuit board assembly that includes a stator assembly comprising aplurality of stator elements arranged about the shaft on a surface ofthe first circuit board assembly; a second circuit board assemblyrotationally coupled to the shaft, wherein the second circuit boardassembly includes a rotor assembly comprising a plurality of rotorelements arranged about the shaft on a surface of the second circuitboard assembly such that the plurality of rotor elements are alignedwith and spaced apart from the plurality of stator elements; a lightranging device coupled to rotate with the second circuit board assembly,the light ranging device including a light source configured to transmitlight pulses to objects in a surrounding environment, and detectorcircuitry configured to detect reflected portions of the light pulsesthat are reflected from the objects in the surrounding environment andto compute ranging data based on the reflected portion of the lightpulses; and a stator driver circuit disposed on either the second or thefirst circuit board assemblies and configured to provide a drive signalto the plurality of stator elements, thereby imparting anelectromagnetic force on the plurality of rotor elements to drive arotation of the second circuit board assembly about the shaft.

In some embodiments a light ranging system includes a stationaryenclosure having an optically transparent window and a base; a hollowshaft disposed within the enclosure; a bearing system coupled to thehollow shaft; a first circuit board assembly disposed within theenclosure and parallel with a first plane perpendicular to the hollowshaft, the first circuit board assembly including a stator assemblycomprising a plurality of evenly spaced stator elements arrangedannularly about the shaft on a surface of the first circuit boardassembly; a second circuit board assembly disposed within the enclosureparallel to the first plane and rotationally coupled to the shaft by thebearing system, wherein the second circuit board assembly includes arotor assembly comprising a plurality of evenly spaced rotor elementsarranged annularly about the shaft on a surface of the second circuitboard assembly such that the plurality of rotor elements are alignedwith and spaced apart from the plurality of stator elements; a lightranging device coupled to rotate with the second circuit board assemblywithin the stationary enclosure, the light ranging device including alight source configured to transmit light pulses through the window toobjects in a surrounding environment, and detector circuitry configuredto detect reflected portions of the light pulses received through thewindow that are reflected from the objects in the surroundingenvironment and to compute ranging data based on the reflected portionof the light pulses; and a stator driver circuit disposed on either thesecond or the first circuit board assemblies and configured to provide adrive signal to the plurality of stator elements, thereby imparting anelectromagnetic force on the plurality of rotor elements to drive arotation of the second circuit board assembly and the light rangingdevice about the shaft.

According to some embodiments a light ranging system includes a housing;a shaft defining an axis of rotation; a first circuit board assemblydisposed within and coupled to the housing in a fixed relationship suchthat the first circuit board assembly is aligned along a first planeperpendicular to the axis of rotation, the first circuit board assemblyincluding a plurality of first circuit elements disposed on a firstcircuit board; a second circuit board assembly spaced apart from thefirst circuit board assembly within the housing in a second planeparallel to the first plane and rotationally coupled to the shaft suchthat the second circuit board assembly rotates about the axis ofrotation, the second circuit board assembly including a plurality ofsecond circuit elements disposed on a second circuit board and alignedwith and configured to function in wireless cooperation with at leastone of the first plurality of circuit elements; and a light rangingdevice electrically connected to and coupled to rotate with the secondcircuit board assembly, the light ranging device configured to transmitlight pulses to objects in a surrounding environment, to detectreflected portions of the light pulses that are reflected from theobjects in the surrounding environment, and to compute ranging databased on the reflected portion of the light pulses.

In some embodiments, a light ranging system includes an enclosure havingan optically transparent window; a shaft defining an axis of rotationthrough the enclosure; a first circuit board assembly disposed withinand fixedly coupled to the enclosure and aligned perpendicular to theaxis of rotation; a second circuit board assembly disposed within theenclosure and spaced apart from and in an opposing relationship with thefirst circuit assembly, the second circuit board assembly rotatablycoupled to the shaft; a light ranging device coupled to the secondcircuit board assembly in a fixed relationship such that the lightranging device rotates with the second circuit board assembly around theshaft; an annular encoder comprising an annular encoder strip mounted onone of the first or second circuit boards and an encoder reader mountedon the other of the first or second circuit boards at a location facingand opposite the annular encoder strip; a wireless communication systemcomprising a first annular wireless communication component mounted tothe first circuit board and a second annular wireless communicationcomponent mounted to the second circuit board at a location facing andopposite the first annular wireless communication component; and anannular wireless power transfer system comprising an annular wirelesspower transmitter mounted to the first circuit board and an annularwireless power receiver mounted to the second circuit board at alocation facing and opposite the annular wireless power transmitter.

In some embodiments, a light ranging system includes an enclosure havingan optically transparent window; a shaft defining an axis of rotationthrough the enclosure; a first circuit board assembly disposed withinand fixedly coupled to the enclosure and aligned perpendicular to theaxis of rotation; a second circuit board assembly disposed within theenclosure and spaced apart from and in an opposing relationship with thefirst circuit assembly, the second circuit board assembly rotatablycoupled to the shaft; a light ranging device mounted to the secondcircuit board assembly such that the light ranging device rotates withthe second circuit board assembly around the shaft, the light rangingdevice configured to transmit light pulses to objects in a surroundingenvironment, to detect reflected portions of the light pulses that arereflected from the objects in the surrounding environment, and tocompute ranging data based on the reflected portion of the light pulses;an annular encoder comprising an annular encoder strip mounted on one ofthe first or second circuit boards and an encoder reader mounted on theother of the first or second circuit boards at a location facing andopposite the annular encoder strip; a wireless communication systemcomprising a first annular wireless communication component mounted tothe first circuit board and a second annular wireless communicationcomponent mounted to the second circuit board at a location facing andopposite the first annular wireless communication component; an electricmotor including a stator assembly comprising a plurality of statorelements arranged about the shaft on a surface of the first circuitboard assembly and a rotor assembly comprising a plurality of rotorelements arranged about the shaft on a surface of the second circuitboard assembly such that the plurality of rotor elements disposed at alocation facing and opposite the plurality of stator elements; a statordriver circuit disposed on either the second or the first circuit boardassemblies and configured to provide a drive signal to the plurality ofstator elements, thereby imparting an electromagnetic force on theplurality of rotor elements to drive a rotation of the second circuitboard assembly about the shaft; and an annular wireless power transfersystem comprising an annular wireless power transmitter mounted to thefirst circuit board and an annular wireless power receiver mounted tothe second circuit board at a location facing and opposite the annularwireless power transmitter.

According to some embodiments a light ranging system includes a shafthaving a longitudinal axis; a light ranging device configured to rotateabout the longitudinal axis of the shaft, the light ranging deviceincluding a light source configured to transmit light pulses to objectsin a surrounding environment, and detector circuitry configured todetect reflected portions of the light pulses that are reflected fromthe objects in the surrounding environment and to compute ranging databased on the reflected portion of the light pulses; a base subsystemthat does not rotate about the shaft; and an optical communicationssubsystem configured to provide an optical communications channelbetween the base subsystem and the light ranging device, the opticalcommunications subsystem including one or more turret opticalcommunication components connected to the detector circuitry and one ormore base optical communication components connected to the basesubsystem.

In some embodiments a light ranging system includes a housing having anoptically transparent window; a hollow shaft having a longitudinal axisdisposed within the housing; a light ranging device disposed within thehousing and configured to rotate about the longitudinal axis of theshaft, the light ranging device including a light source configured totransmit light pulses through the optically transparent window toobjects in a surrounding environment, and detector circuitry configuredto detect reflected portions of the light pulses through the opticallytransparent window reflected from the objects in the surroundingenvironment and to compute ranging data based on the reflected portionof the light pulses; a base subsystem disposed within the housing thatdoes not rotate about the shaft; and an optical communications subsystemdisposed within the housing and configured to provide an opticalcommunications channel between the base subsystem and the light rangingdevice, the optical communications subsystem including a first opticalchannel disposed within the hollow shaft and a second optical channelarranged annularly outside the hollow shaft.

In some embodiments, a light ranging system includes a housing having anoptically transparent window; a hollow shaft having a longitudinal axisdisposed within the housing; a light ranging device disposed within thehousing and configured to rotate about the longitudinal axis of theshaft, the light ranging device including a light source configured totransmit light pulses through the optically transparent window toobjects in a surrounding environment, and detector circuitry configuredto detect reflected portions of the light pulses through the opticallytransparent window reflected from the objects in the surroundingenvironment and to compute ranging data based on the reflected portionof the light pulses; a base subsystem disposed within the housing thatdoes not rotate about the shaft; a first optical communication channelconfigured to optically transmit data between the light ranging deviceand the base subsystem through the hollow shaft, the first opticalcommunication channel including a first optical component coupled tocircuitry coupled to rotate with the light ranging device and a secondoptical component coupled to circuitry disposed on the base subsystem;and a second, annular optical communication channel surrounding thehollow shaft and configured to optically transmit data between the lightranging device and the base subsystem, the annular optical communicationchannel including a first annular optical component coupled to circuitrycoupled to rotate with the light ranging device and a second annularoptical component coupled to circuitry disposed on the base subsystem.

According to some embodiments, a light ranging device can include alight emitting module and a light sensing module. The light emittingmodule can include a light source configured to transmit light pulses toobjects in a surrounding environment. The light sensing module caninclude a lens housing; a bulk lens system coupled to the lens housingand configured to receive light from the surrounding environment andfocus the received light to a focal plane, the bulk lens systemcomprising a first lens, a second lens, and a third lens mounted in thelens housing; wherein the first lens, the second lens, or the first lensand the second lens are plastic; and wherein the third lens is glass; anarray of photosensors configured to receive light from the bulk lenssystem and detect reflected portions of the light pulses that arereflected from the objects in the surrounding environment; and a mountthat mechanically couples the lens housing with the array ofphotosensors, wherein the lens housing, the bulk lens system, and themount are configured to passively focus light from the bulk lens systemonto the array of photosensors over a temperature range. In someinstances the lens housing, the bulk lens system, and the mount areconfigured to match, as a function of temperature, a focal length of thelens system with an expansion coefficient of the lens housing and withan expansion coefficient of the mount so that light is passively focusedonto the array of photosensors over the temperature range, such as −5degrees C. to 70 degrees C.

In some embodiments, a light ranging system includes an enclosure havingan optically transparent window, a light ranging device disposed withinthe enclosure and circuitry configured to compute ranging data. Thelight ranging device can include an optical transmitter comprising abulk transmitter lens system and a plurality of transmitter channels,each channel including a light emitter configured to generate andtransmit pulses of narrowband light through the bulk transmitter opticand through the optically transparent window into a field external tothe light ranging system; and an optical receiver comprising a bulkreceiver lens system, a lens housing and a plurality of micro-opticreceiver channels, each micro-optic channel including an aperturecoincident with a focal plane of the bulk receiver optic, a collimatinglens behind the aperture, an optical filter behind the collimating lensand a photosensor responsive to incident photons passed through theaperture into the collimating lens and through the filter. The bulkreceiver lens system can include a first lens, a second lens, and athird lens mounted in the lens housing; wherein the first lens, thesecond lens, or the first lens and the second lens are plastic;

the third lens is glass; and a coefficient of thermal expansion (CTE) ofthe lens housing is matched, over a temperature range, with the bulkreceiver lens system so that the focal plane is stable relative to eachphotosensor in the plurality of micro-optic receiver channels over thetemperature range. In some instances the temperature range is from 20degrees C. to 70 degrees C. and in some instances the temperature rangeis from −5 degrees C. to 70 degrees C.

In some embodiments an image sensing device is provided. The imagesensing device can include a lens housing; a bulk lens systemmechanically coupled to the lens housing and configured to receive lightfrom the surrounding environment and focus the received light to a focalplane. The bulk lens system can include a first lens, a second lens, anda third lens mounted in the lens housing, wherein the first lens, thesecond lens, or the first lens and the second lens are plastic andwherein the third lens is glass. The image sensing device can furtherinclude an array of photosensors configured to receive light from thebulk lens system, and a mount that mechanically couples the lens housingwith the array of photosensors. The coefficient of thermal expansion(CTE) of the lens housing can be matched, over a temperature range, withthe bulk lens system so that the focal plane is stable relative to thearray of photosensors over the temperature range. In some instances thetemperature range is from 20 degrees C. to 70 degrees C. and in someinstances the temperature range is from −5 degrees C. to 70 degrees C.And, in some embodiments, a CTE of the mount is matched with the CTE ofthe lens housing.

These and other embodiments of the invention are described in detailbelow. Additionally, other aspects and advantages of various embodimentsof the disclosure will become apparent from the following detaileddescription taken in conjunction with the accompanying drawings whichillustrate, by way of example, the principles of the describedembodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1B show a rotating light ranging system and a non-rotating,solid-state light ranging system, respectively, that can be used inautomotive applications according to some embodiments;

FIGS. 2A-2B show high level block diagrams of rotating and solid-stateLIDAR systems, respectively, according to some embodiments;

FIG. 3 illustrates a more detailed block diagram of a rotating LIDARsystem 300 according to some embodiments like those described above inreference to FIG. 2A;

FIGS. 4A and 4B show an illustrative example of the light transmissionand detection process for a light ranging system according to someembodiments, with a focus on the emitter array and sensor array thatform an arrangement of emitter-sensor channels, as introduced above inreference to FIG. 2;

FIGS. 5A-5B show a rotating LIDAR system 500 in accordance with one ormore embodiments;

FIGS. 6A-6C show cross-sectional views of a LIDAR system in accordancewith one or more embodiments;

FIG. 6D shows a top view of a stator board in accordance with one ormore embodiments;

FIG. 6E shows a bottom view of a rotor board in accordance with one ormore embodiments;

FIG. 6F is a simplified cross-sectional view of a portion of amulti-coil wireless power receiver positioned within an annular ferritechannel according to some embodiments;

FIG. 7 shows an exploded view of the lower circuit board assembly toillustrate the assembly process of the compact LIDAR system according tocertain embodiments;

FIGS. 8A and 8B show an exploded view of a LIDAR system according tosome embodiments;

FIGS. 9A-9C show a perspective view, a front view, and a zoomed frontview, respectively, of a light ranging device 900 according to certainembodiments;

FIG. 10 shows an optical block diagram of a light ranging device 1000showing both the optical systems for a Rx module 1001 and a Tx module1003 according to certain embodiments;

FIG. 11A shows a top view of a micro-optics package according to certainembodiments;

FIG. 11B shows a cross-section of a single micro-optic receiver channelaccording to some embodiments;

FIG. 12A-12B shows top views of a SPAD-based detector according to someembodiments;

FIGS. 13A and B show simplified top and side views of a VCSEL chiptransmitter according to some embodiments;

FIG. 14 depicts a simplified schematic of an embodiment of a LIDAR bulkoptical system;

FIGS. 15A, 15B, and 15C depict an embodiment of a bulk optics lensassembly;

FIGS. 16A-16E depicts various views of an embodiment of a lens assembly;

FIG. 17A-17D, depict a cross sections of embodiment of the lenses of alens assembly; and

FIG. 18 depicts an embodiment of a lens assembly with three lenses.

TERMS

Unless defined otherwise, technical and scientific terms used hereinhave the same meaning as commonly understood by a person of ordinaryskill in the art. The following definitions, however, are provided tofacilitate understanding of certain terms used frequently and are notmeant to limit the scope of the present disclosure. Abbreviations usedherein have their conventional meaning within the relevant arts.

The term ranging data may refer to any data that can be transmitted froma laser ranging device, e.g., a turret component of a rotating LIDARsystem. Examples of ranging data include range information, e.g.distance to a given target point at a certain angle (azimuth and/orzenith), range-rate or velocity information, e.g. the derivative of theranging data with respect to time, and also operational information suchas signal-to-noise ratio (SNR) of return or signal intensity, targetreflectivity, ambient NIR levels coming from each pixel field of view,diagnostic information including temperature, voltage levels, etc. Insome embodiments, ranging data can include RGB information from an RGBcamera that is located in the turret, e.g., a high speed read-out camerasuch as a line scan camera or thermal imager.

The term turret can refer to the rotating part or portion of a rotatingLIDAR system. Turret components include any rotating component orcircuit boards in the turret portion of the LIDAR system and can includeone or more components located in a light ranging device and/or one ormore components located on a rotating circuit board of a rotaryactuator.

In the context of a rotating LIDAR system (sometimes referred to hereinas a “spinning LIDAR system”), the term base can refer to thenon-rotating part or non-rotating portion of the rotating LIDAR system.Base components include any non-rotating component or circuit boards inthe base portion of the LIDAR system and can include one or morecomponents located in a base assembly and/or one or more componentslocated on a non-rotating circuit board of a rotary actuator.

The terms upper and lower refer to the position, or relative position,of components along the axis of rotation of a LIDAR system. In someembodiments, upper components, also referred to as turret components,are located on the turret of the LIDAR system while lower components,also referred to as base components, are located on the base of theLIDAR system.

The term ring includes not just circular shapes but also shapes that areslightly non-circular, e.g., elliptical, and arranged circumferentiallyaround a central axis, including perturbations or oscillations (e.g.,wavy) at a circumference.

One or more shapes that are referred to as symmetric can include bothperfectly symmetric shapes as well as shapes that are generally but notperfectly symmetric. Arrangements of electronic components describedherein may operate most efficiently in a symmetric configuration,however, the term symmetric does not exclude those configurations thatare slightly asymmetric, or have a slight deviation from symmetric evenif those configurations do not result in the optimal operationalconfiguration.

The term parallel is not limited to perfectly parallel but includes alsothose geometrical arrangements and configurations that are substantiallyparallel as a result of manufacturing variations, e.g., two elementsthat are referred to herein as being parallel may have an angle between−5 and 5 degrees or −1 and 1 degrees between the two elements dependingon the manufacturing tolerance employed.

The term perpendicular is not limited to perfectly perpendicular butincludes also those geometrical arrangements and configurations that aresubstantially perpendicular as a result of manufacturing variations,e.g., two elements that are referred to herein as being perpendicularmay have an angle between 85 and 95 degrees between the two elements.

The term photosensor (or just sensor) refers to a sensor that canconvert light into an electrical signal (e.g., an analog electricalsignal or binary electrical signal). An avalanche photodiode (APD) isone example of a photosensor. A single photosensor can include aplurality of smaller “photodetectors”. Thus, a plurality ofsingle-photon avalanche diodes (SPADs) can be another example of aphotosensor where each individual SPAD in the plurality of SPADs (e.g.,each SPAD in an array of SPADs) can be referred to as a photodetector.The term sensor array can sometimes refer to a sensor chip that includesan array of multiple sensors. Additionally, the term pixel is sometimesused interchangeably with photosensor or sensor.

The term transmitter can refer to a structure that includes one or morelight transmitting elements, e.g., LED, laser, VCSEL, and the like. Theterm transmitter can also include a transmitter chip that includes anarray of transmitters, sometimes referred to as an emitter array.

The term bulk optic(s) refers to single lenses and/or lens assembliesthat include one or more macroscopically-sized optics, e.g., withdiameters on the order of centimeters or greater, such as those used incommercially available camera lenses and microscope lenses. In thisdisclosure, the term bulk optics is contrasted with the termmicro-optics which refers to optical elements or arrays of opticalelements having individual element diameters that are on the order of afew micrometers to a few millimeters in size or smaller. In general,micro-optics can modify light differently for different emitters and/ordifferent detectors of an array of emitters or an array of detectors,whereas the bulk optics modify light for the entire array.

As used herein, the term image space telecentric optics module refers toan optical system (bulk or otherwise) where, at the image plane, all (orsubstantially all) of the chief rays from within the aperture of thelenses are incident on the image plane “straight on”, or at a zero angleof incidence, within a specified tolerance (e.g., +/−2 degrees).

DETAILED DESCRIPTION

According to certain embodiments, methods and systems disclosed hereinrelate to a compact light ranging and detection (LIDAR) system andmethods of assembly of a compact LIDAR system. The LIDAR system caninclude a modular light ranging device and an optional highly compactand integrated rotary actuator. The modular light ranging device canoperate as a stand-alone non-rotating solid state LIDAR or, if connectedto the integrated rotary actuator, can operate as part of a turret of arotating LIDAR. The light ranging device can include a lighttransmission module (sometimes referred to as a “light emitting module”)for illuminating objects in a field located around the light rangingmodule and also includes a light sensing module for sensing reflected orscattered portions of the illuminating light pulses for use in computinga 3D depth image. The light ranging module can also include a detectorchip (e.g., a CMOS chip) that includes an array of photosensors, each ofwhich can be, for example, an array of SPADs.

In some embodiments, the rotary actuator includes an upper circuit boardassembly (also referred to herein as a turret, or rotating circuit boardassembly) and a base circuit board assembly (also referred to herein asa stationary circuit board assembly). The various circuit boards of therotary actuator can be highly integrated in the sense that many of thefunctional and/or supporting electronic and optical components of theLIDAR system can be mounted directly to one or more boards of the rotaryactuator. For example, the base controller of the LIDAR system that cancontrol various emission parameters of the light transmission module canbe mounted on a board of the base circuit board assembly of the rotaryactuator. Furthermore, power can be provided to the light ranging moduleby way of a wireless power transmission system that is also integratedonto a board of the rotary actuator. Communication between the basecontroller and the light ranging module and vice versa can be enabled byway of an optical uplink channel and an optical downlink channel wherethe electrical and optical components that support the opticaluplink/downlink channels are also integrated onto one or more circuitboards of the rotary actuator.

In some embodiments, these same boards include electric motor componentsintegrated onto one or more surfaces of the upper and lower circuitboard assemblies of the rotary actuator. For example, an electric motorstator can be bonded directly to a surface of the lower circuit boardassembly of the rotary actuator along with other electrical components,e.g., a group of optical uplink transmitters, an optical downlinkreceiver, and a wireless power transmitter. Likewise, an electric motorrotor can be bonded directly to a surface of the upper circuit boardassembly of the rotary actuator along with other electrical components,e.g., a group of optical uplink receivers, an optical downlinktransmitter, an optical or magnetic rotary encoder reader, and awireless power receiver.

In some embodiments, the upper circuit board assembly can include one ormore connectors, also bonded to a surface of the upper circuit boardassembly, to connect the light ranging module to the upper circuit boardassembly. Additionally, the rotary actuator can also include additionalcomputational resources, one or more FPGAs, ASICs, microprocessors, andthe like, that can be used by the light ranging module to perform dataprocessing on the acquired data.

In view of the high level of systems integration in the compact LIDARdisclosed herein, a fully functioning system can be assembled by simplyattaching the light ranging module to the rotary actuator. There is noneed for a separate electric motor module, separate communicationsmodule, separate power modules, etc.

In some embodiments, the architecture of the rotary actuator lendsitself to an elegant method of assembly. For example, the system can bearchitected such that the electrical components, includingcommunications components, electric motor components, and wireless powercomponents are arranged circumferentially and concentrically around acentral axis of the system or even coaxially with the axis of thesystem. The central axis can also be collinear with the axis of rotationof the upper circuit board assembly, or turret. One or more boards ofthe rotary actuator can include a central hole that is configured toreceive a shaft that can be attached (directly or indirectly) to a lowerportion, or base, of a fixed enclosure. In some embodiments, the shaftdefines the axis of rotation of the system and one or more bearingsattached thereto provide for rotational movement of the upper circuitboard assembly relative to the lower circuit board assembly.

In view of the above architecture, assembly of the rotary actuator insome embodiments can be reduced to dropping successive boards in placeon the shaft. Because a subset of the electrical components (such as thecommunications components, electric motor components, and wireless powercomponents) are arranged circumferentially around a central axis of thesystem these systems can operate effectively without the need forcomplex alignment procedures once the assembly is complete.

In some embodiments, the system employs a thermally stable image-spacetelecentric optics module employed within the light transmission moduleor the light sensing module, or both. The thermally stable image-spacetelecentric optics module can be engineered to have an image plane thatis stable in space relative to transmitter or sensor chip that includesan array of transmitters and/or sensors of the light transmission moduleor light sensing module, respectively. The coefficients of thermalexpansion of a lens housing and of the optical elements within the lenshousing, along with the change in refractive index with respect totemperature, can be chosen to provide for the thermally stable imageplane. In various embodiments, the individual optics in the opticalsystem may be glass and/or plastic to provide for an economical yetthermally stable design.

A modular light ranging device according to some embodiments of thedisclosure includes a set of vertical-cavity surface-emitting lasers(VCSELs) as illumination sources that emit pulses of radiation into afield and includes arrays of single-photon avalanche diode (SPAD)detectors as a set of pixels (photosensors) that detect radiationreflected or scattered from a surface in the field. As stated above,SPADs have a relatively low dynamic range as compared to APDs that areused in some currently available LIDAR sensors. The low dynamic rangeinherent to SPADs is due, in part, to the physics of how a SPAD detectsa photon—they are so-called Geiger mode devices that, for each photondetection event, produce a binary electrical signal (photon detected ornot detected) in the form of an avalanche current pulse. Using VCSELs asthe emitters and SPADs as the detectors enables multiple measurements tobe taken at the same time (i.e., the VCSEL emitters can be firedsimultaneously) and also enables the set of emitters and the set ofphotosensors to each be fabricated using standard CMOS processes on asingle chip, greatly simplifying the manufacturing and assembly process.Using VCSELs and SPADs in certain embodiments presents challenges,however, that various embodiments of the invention overcome. Forexample, VCSELs are much less powerful than the lasers used in somecurrently available LIDAR sensors and SPADs are much less efficient thanthe detectors used in some LIDAR sensors. To address these challenges,as well as challenges presented by firing multiple emitterssimultaneously, certain embodiments of the disclosure can includeoptical components to enhance the brightness of the VCSEL emitter aswell as various optical components (e.g., lenses, filters, and anaperture layer), which may work in concert with multiple arrays ofSPADs, each array corresponding to a different photosensor, as describedherein.

I. Illustrative Automotive LIDAR System

FIGS. 1A-1B show automotive light ranging devices, also referred toherein as LIDAR systems, according to some embodiments. The automotiveapplication for the LIDAR systems is chosen here merely for the sake ofillustration and the sensors described herein may be employed in othertypes of vehicles, e.g., boats, aircraft, trains, etc., as well as in avariety of other applications where 3D depth images are useful, such asmedical imaging, geodesy, geomatics, archaeology, geography, geology,geomorphology, seismology, forestry, atmospheric physics, laserguidance, airborne laser swath mapping (ALSM), and laser altimetry.According to some embodiments, a LIDAR system, e.g., scanning LIDARsystem 100 and/or solid state LIDAR system 120, can be mounted on theroof of a vehicle 105 as shown in FIGS. 1A and 1B. In other embodimentsone or more LIDAR sensors can be mounted on other locations of a vehicleincluding, but not limited to, the front or back of the vehicle, thesides of the vehicle and/or corners of the vehicle.

The scanning LIDAR system 100 shown in FIG. 1A can employ a scanningarchitecture, where the orientation of the LIDAR light transmissionmodule 102 (e.g., light source for emitting laser pulses) and/or lightsensing module 104 (e.g., detector circuitry for detecting reflectedpulses to determine distance to an object) can be scanned around one ormore fields of view 110 within an external field or scene that isexternal to the vehicle 105. In the case of the scanning architecture,the emitted light 112 can be scanned over the surrounding environment asshown. For example, the output beam(s) of one or more light sources(such as infrared or near-infrared pulsed IR lasers, not shown) locatedin the scanning LIDAR system 100, can be scanned, e.g., rotated, toilluminate a scene around the vehicle. In some embodiments, thescanning, represented by rotation arrow 115, can be implemented bymechanical means, e.g., by mounting the light emitters to a rotatingcolumn or platform. In some embodiments, the scanning can be implementedthrough other mechanical means such as through the use of galvanometers.Chip-based steering techniques can also be employed, e.g., by usingmicrochips that employ one or more MEMS based reflectors, e.g., such asa digital micro-mirror (DMD) device, a digital light processing (DLP)device, and the like. In some embodiments, the scanning can beeffectuated through non-mechanical means, e.g., by using electronicsignals to steer one or more optical phased arrays.

For a stationary architecture, like the solid state LIDAR system 120shown in FIG. 1B, one or more solid state LIDAR subsystems (e.g., lighttransmission module 122 and light sensing module 124) can be mounted tothe vehicle 105. Each solid state LIDAR unit can face a differentdirection (possibly with partially and/or non-overlapping fields ofviews between units) so as to capture a composite field of view that islarger than each unit is capable of capturing on its own.

In either the rotating or stationary architectures, objects within thescene can reflect portions of the light pulses that are emitted from theLIDAR light sources. One or more reflected portions then travel back tothe LIDAR system and can be detected by the detector circuitry. Forexample, reflected portion 114 can be detected by detector circuitry104. The light transmission module can be disposed in the same housingas the light sensing module. Aspects of the scanning system andstationary system are not mutually exclusive and thus can be used incombination. For example, the individual LIDAR subsystems 122 and 124 inFIG. 1B can employ steerable emitters such as a MEMS oscillating mirroror the whole composite unit may rotate through mechanical means therebyscanning the entire scene in front of the LIDAR system, e.g., from fieldof view 130 to field of view 132.

FIGS. 2A-2B show high level block diagrams of a rotating LIDAR system200 and a stationary solid state LIDAR system 230, respectively,according to some embodiments. Both systems employ a light rangingdevice 210 that includes a light transmission module 212 and a lightsensing module 214. The light transmission and sensing modules 212 and214 can each include bulk optics 215, e.g., a multi-element lensassembly positioned at the input/output of the sensing and transmissionmodules, respectively. Light transmission module 212 can further includea micro-optics array and optional notch filter element (not shown) thatis located between the bulk optics 215 and light emitter circuitry 216.In some embodiments, light emitter circuitry 216 includes a chip-scalearray of light sources, such as an array of vertical cavity surfaceemitting lasers (VCSELs) on an Indium Gallium Arsenide (InGAs)substrate. Light sensing module 214 can also include a micro-opticsarray and notch filter element (not shown) that is located between thebulk optics 215 and light detector circuitry 218. In some embodiments,light detector circuitry 218 can includes a chip-scale array of photondetectors, such as an array of single photon avalanche diodes (SPADS)fabricated in a CMOS technology. Other detector technologies can beemployed as well, e.g., avalanche photodiodes, CCD image sensors, CMOSphotodiode image sensors, cavity enhanced photodetectors, surfaceenhanced photodetectors, and the like.

Turning to FIG. 2A, in rotating LIDAR system 200, light ranging device210 can be electrically connected to a turret circuit board assembly 222(also referred to herein as an upper circuit board assembly or rangingcircuit board assembly). Circuit board assembly 222 can be consideredranging to the extent that it is connected to light ranging device 210.As described in more detail in FIG. 3 below, the turret circuit boardassembly 222 can include a number of circuit elements including one ormore processors and memory. For example, the turret circuit boardassembly 222 can include a field programmable gate array (FPGA) and orone or more application specific integrated circuits (ASICs) that aretailored to provide certain LIDAR functionality. In some embodiments,the light ranging device 210 can be hard wired to the turret circuitboard assembly 222 via a multi-pin electrical connector or may bewirelessly connected, e.g., through a communication channel employingoptical or RF connections, to the turret circuit board assembly 222.

Turret circuit board assembly 222 can be disposed directly above a basecircuit board assembly 226. In some embodiments, the base circuit boardassembly 226 can wirelessly transmit power to the turret circuit boardassembly 222 to, for example, power light ranging device 210 and anyother associated circuitry (e.g., ASICS, FPGAs, communications circuitsand the like). In addition, optical, inductive, and/or capacitivecommunications channels can connect the base circuit board assembly 226to turret circuit board assembly 222 thereby allowing for the lightranging device 210 to be controlled via contactless data transfer fromthe base circuit board assembly.

In the embodiment shown in FIG. 2A, turret circuit board assembly 222 isrotationally coupled to base circuit board assembly 226 through arotational coupler 224. Rotational coupler 224 enables light rangingdevice 210 and turret circuit board assembly 222 to rotate a full 360degrees within a housing 220 of LIDAR system 200. Rotation of the lightranging device 210 allows the system to acquire data that can be used toconstruct a full 360 field-of-view 3D map of a volume around the device.In some embodiments, the base circuit board assembly 226 can be coupledto the housing 220, for example, by way of a mechanical bracket andscrews (not shown), such that base circuit board assembly 226 is heldstationary and does not rotate relative to housing 220. Housing 220 canbe a waterproof housing that protects light ranging device 210 and otherinternal components of LIDAR system 200 from moisture and variouselements of the environment that LIDAR system 200 operates within.

Rotational coupler 224 can be implemented in a number of different waysin various embodiments. For example, some embodiments can employ a shaftand bearing structure. In some embodiments, rotational coupler 224 alsoincludes one or more components for a rotary actuator that not onlyallows for rotational movement but also drives the rotational movementof the turret circuit board assembly 222. For example, an electric motorrotor assembly including an arrangement of rotor elements (e.g.,permanent magnets), can be directly integrated into the turret circuitboard assembly 222, and an electric motor stator assembly including anarrangement of stator elements, such as solenoid coils, can be directlyintegrated into the base circuit board assembly 226. In suchembodiments, where one or more rotary actuation components areintegrated into the base circuit board assembly 226 and/or the turretcircuit board assembly 222, a separate module for rotary actuation is nolonger needed. As a result, embodiments of the LIDAR system disclosedherein can have a more compact form factor and much simplified assemblyprocess than spinning LIDAR systems that employ a separate electricmotor module.

FIG. 2B is a simplified block diagram of a stationary solid state LIDARsystem 230 according to some embodiments. Like rotating LIDAR system 200shown in FIG. 2A, stationary solid state LIDAR system 230 includes alight ranging device 210 housed within a waterproof housing 240. Lightranging device 210 can be directly connected to a base circuit boardassembly 232 within housing 240. Since system 230 does not rotate lightranging device 210, there is no need for a separate rotating turretcircuit board assembly or a rotational coupler. Accordingly, thecircuitry that was previously distributed amongst the turret circuitboard assembly 222 and the base circuit board assembly 226 can beintegrated entirely into the single base circuit board assembly 232and/or shared amongst the circuitry associated with the light sensingmodule 214 and/or transmission module 212.

In some embodiments, for either of the embodiment shown in FIGS. 2A-2B,the hardware and software/firmware for performing one or moreLIDAR-specific operations (e.g., photon time series accumulationfollowed by peak detection and ranging data computation and output) canbe incorporated into the circuitry of light ranging device 210 and/orone or more of the circuit board assemblies (e.g., turret circuit boardassembly 222 and/or base circuit board assembly 226 for LIDAR system200, or base circuit board assembly 232 for LIDAR system 230). Forexample, in some embodiments, the light detector circuitry 218 may alsoinclude an ASIC that is integrated onto the same substrate as the arrayof SPADs. In such a situation, the light ranging device 210 is modularin the sense that a reprogramming/reconfiguring of the software/firmwarecan allow the light ranging device 210 to operate as part of a rotatingLIDAR system (like LIDAR system 200 shown in FIG. 2A) or as astand-alone solid state LIDAR system (like LIDAR system 230 shown inFIG. 2B). As already mentioned above, circuitry can be employed (e.g.,MEMS, DMD, optical phased arrays, and the like) that will also allow forbeam steering without the need for a mechanical rotational actuator.Accordingly, the modular design of the system disclosed herein resultsin a highly adaptable system that can fit user needs without expensiveand time consuming redesign of the overall hardware and mechanicalarchitecture.

II. Detailed Block Diagram

FIG. 3 illustrates a more detailed block diagram of a rotating LIDARsystem 300 according to some embodiments like those described above inreference to FIG. 2A. More specifically, rotating LIDAR system 300 canoptionally employ a rotary actuator with wireless data and powertransmission and reception capabilities. In some embodiments, the rotaryactuator includes a rotor that is integrated onto a surface of arotating circuit board and a stator that is integrated onto a surface ofa stationary circuit board and both board assemblies are equipped withwireless power and data transfer capabilities.

Rotating LIDAR system 300 shown in FIG. 3 includes two main modules: alight ranging device 320 and a rotary actuator 315 described in detailbelow. Additionally, rotating LIDAR system 300 can interact with one ormore instantiations of user interface hardware and software 305. Thedifferent instantiations of user interface hardware and software 305 canvary and may include, e.g., a computer system with a monitor, keyboard,mouse, CPU and memory; a touch-screen in an automobile; a handhelddevice with a touch-screen; or any other appropriate user interface. Theuser interface hardware and software 305 may be local to the object uponwhich rotating LIDAR system 300 is mounted but can also be a remotelyoperated system. For example, commands and data to/from rotating LIDARsystem 300 can be routed through a cellular network (LTE, etc.), apersonal area network (Bluetooth, Zigbee, etc.), a local area network(WiFi, IR, etc.), or a wide area network such as the Internet.

The user interface hardware and software 305 can present the LIDAR datafrom the device to the user but can also allow a user to control therotating LIDAR system 300 with one or more commands. Example commandscan include commands that activate or deactivate the LIDAR system,specify photo-detector exposure level, bias, sampling duration and otheroperational parameters (e.g., for emitted pulse patterns and signalprocessing), specify light emitters parameters such as brightness. Inaddition, commands can allow the user to select the method fordisplaying results. The user interface can display LIDAR system resultswhich can include, e.g., a single frame snapshot image, a constantlyupdated video image, and/or a display of other light measurements forsome or all pixels such as ambient noise intensity, return signalintensity, calibrated target reflectivity, target classification (hardtarget, diffuse target, retroreflective target), range, signal to noiseratio, target radial velocity, return signal temporal pulse width,signal polarization, noise polarization, and the like. In someembodiments, user interface hardware and software 305 can trackdistances (proximity) of objects from the vehicle, and potentiallyprovide alerts to a driver or provide such tracking information foranalytics of a driver's performance.

In some embodiments, the LIDAR system can communicate with a vehiclecontrol unit 310 and one or more parameters associated with control of avehicle can be modified based on the received LIDAR data. For example,in a fully autonomous vehicle, the LIDAR system can provide a real time3D image of the environment surrounding the car to aid in navigation. Inother cases, the LIDAR system can be employed as part of an advanceddriver-assistance system (ADAS) or as part of a safety system that, forexample, can provide 3D image data to any number of different systems(e.g., adaptive cruise control, automatic parking, driver drowsinessmonitoring, blind spot monitoring, collision avoidance systems, etc).When a vehicle control unit 310 is communicably coupled to light rangingdevice 320, alerts can be provided to a driver or the proximity of anobject can be tracked and/or displayed.

Light ranging device 320 includes light sensing module 330, lighttransmission module 340 and light ranging system controller 350. Therotary actuator 315 includes at least two circuit board assemblies, alower circuit board assembly 360 (also referred to herein as a basesubsystem) and an upper circuit board assembly 380 (also referred toherein as a turret subsystem). The lower circuit board assembly 360 canbe mechanically mounted to a fixed portion of an enclosure or housing(not shown) while the upper circuit board assembly 380 is free to rotateabout an axis of rotation, usually defined by a shaft (not representedin FIG. 3) that is also mounted to the enclosure (directly orindirectly). The light ranging device 320 can be mechanically attachedto the rotatable upper circuit board assembly 380 and therefore is freeto rotate within the housing.

While FIG. 3 shows one particular arrangement of components within lightranging device 320 and rotary actuator 315, in some embodiments, certaincomponents may be integrated into one, or the other, module differentlythan shown. As one example, ranging system controller 350, which can be,for example, an FPGA, ASIC, or a more general computing device, like anembedded system or system-on-a-chip (SOC), can be mounted directly(e.g., soldered) to, a printed circuit board that is part of the uppercircuit board assembly 380. In other words, in some embodiments, theparts of the rotary actuator can be integrated within the light rangingdevice 320 and vice versa.

The rotary actuator 315 includes a number of different systems that areintegrated onto one or more printed circuit boards of the lower andupper circuit board assemblies 360 and 380. For example, rotary actuator315 can include a brushless electric motor assembly, an opticalcommunications subsystem, a wireless power transmission subsystem, and abase controller. These systems are formed by pairs of cooperatingcircuit elements with each pair including one or more circuit elementson the lower circuit board assembly 360 operating in cooperation with(e.g., having a function that is complementary to) one or more circuitelements on the upper circuit board assembly 380. Complementaryfunctions include, for example, transmission (Tx) and reception (Rx) ofpower and/or data communication signals as is described in more detailbelow.

The brushless electric motor assembly includes a stator assembly 362integrated onto a printed circuit board of the lower circuit boardassembly 360 and a rotor assembly 382 integrated onto a printed circuitboard of the upper circuit board assembly 380. The rotation of rotorassembly 382 is driven from a drive signal, for example, a three-phasedrive current, that originates from a motor driver circuit 364. In someembodiments, one or more motor control lines connect the motor drivercircuit to the coils of the stator assembly 362 to allow for the drivesignal to be provided to the motor stator. Furthermore, the motor drivercircuit 364 can be electrically connected to a base controller 366 suchthat the base controller 366 can control the rotation rate of the rotorassembly and thus the rotation rate (i.e., frame rate) of the lightranging device 320.

In some embodiments, rotor assembly 382 can rotate at a rate between10-30 Hz. In some embodiments, the rotor assembly 382 can be a passivedevice that includes a series of permanent magnets that are attached toa circuit board of the upper circuit board assembly. These permanentmagnets are either attracted to or repelled by an electromagnetic force,for example, a magnetic force, generated by the coils of the statorassembly to drive a rotation of the upper circuit board assembly 380relative to the lower circuit board assembly 360. The rotationalorientation of the upper circuit board assembly 380 can be tracked by arotary encoder receiver 394, which can track the angular position of theupper circuit board assembly by detecting the passage of one or morefeatures on the rotary encoder 374. A variety of different rotaryencoder technologies can be employed. In some embodiments, rotaryencoder 374 is integrated directly onto a surface of a circuit board ofthe lower circuit board assembly 360.

Rotary actuator 310 can also include a wireless power system thatincludes a wireless power transmitter 372 and a wireless power receiver392 in a configuration referred to herein as a rotary transformer. Powertransmitted from transmitter 372 to wireless power receiver 392 can beconsumed by light ranging device 320 and/or any circuitry needing poweron the turret/upper circuit board assembly. In some embodiments, allpower required by light ranging device 320 is provided through wirelesspower receiver 392 and thus there is no need for a rotary electriccoupler like a slip ring or mercury based device thereby increasingreliability and decreasing cost of the overall system.

Rotary actuator 310 can also include an optical communication subsystemthat includes a number of optical transmitters (e.g., opticaltransmitters 378 and 396) and a number of optical receivers (e.g.,optical receivers 376 and 398) used for bi-directional contactless datatransmission between rotary actuator 315 and light ranging device 320(or to/from any other device or system that is mechanically connected toupper circuit board assembly 380 of the rotary actuator 315). Morespecifically, the optical communication subsystem can include a set ofbase optical communication components that are attached to (e.g.,soldered to) lower circuit board assembly 360 that is part of thestationary base of LIDAR system 300, and can include a set of turretoptical communication components that are attached to (e.g., solderedto) rotating upper circuit board assembly 380 that is part of therotating turret of LIDAR system 300. These optical communicationcomponents provide an uplink data channel for providing optical signals,including control signals, to light ranging device 320 and also providea downlink data channel for providing optical signals, including rangingand operational data, from light ranging device 320 to base controller366, user interface hardware and software 305, and/or the vehiclecontrol unit 310.

A downlink optical communication channel from the upper circuit boardassembly 360 to the lower circuit board assembly 380 can be createdbetween the optical downlink transmitter 396 and the optical downlinkreceiver 376. Light ranging device 320 can be connected directly toupper circuit board assembly 380 and therefore can access the downlinkoptical communication channel to pass ranging and operational data downto lower circuit board assembly 360 for further use. In someembodiments, the data passed down in the optical signals via the opticaldownlink can include range data for individual points (pixels) in thefield (or possibly multiple ranges for a single pixel and angle, e.g.during fog/rain, when looking through glass windows, etc.), azimuth andzenith angle data, signal to noise ratio (SNR) of the return or signalintensity, target reflectivity, ambient near IR (NIR) levels coming fromeach pixel field of view, diagnostic operational information from thelight ranging device such as temperature, voltage levels, etc. Inaddition, data from any other system connected to upper circuit board380 of the rotary actuator can be passed down through the opticaldownlink. For example, data from high speed RGB or thermal cameras, linescan cameras and the like.

An uplink optical communication channel from lower circuit boardassembly 360 can be created between optical uplink transmitter 378 andoptical uplink receiver 398. In some embodiments, control signals fromthe base controller 366 can be passed to light ranging device 320 viathe optical uplink communication channel. For example, in someembodiments, base controller 366 can monitor various temperatures in thedevice (as received from the downlink channel) and can, in the case ofan overheat condition, send an emergency shutdown signal to lightranging device 320 via the uplink channel. In some embodiments, the basecontroller can be a mobile computer, e.g., a programmablesystem-on-a-chip employing an ARM+FPGA architecture with associatedmemory and I/O capability (e.g., Ethernet and the like).

Ranging data can be generated by light ranging device 320 bytransmitting one or more light pulses from light transmission module 340to objects in a field of view surrounding the light ranging device.Reflected portions of the transmitted light are then detected by lightsensing module 330 after some delay time. Based on the delay time,commonly referred to as the “time of flight”, the distance to thereflecting surface can be determined. Other ranging methods can beemployed as well, for example, continuous wave, Doppler, and the like.

Light transmission module 340 can include an emitter array 342 and aTransmit (Tx) optical system 344. Emitter array 342 can be aone-dimensional or two-dimensional array of transmitters, which whencombined with transmit optical system 344 form an array of transmitterchannels behind a bulk imaging optic. These transmitter channels canoptionally include micro-optic structures for beam-shaping,beam-steering, brightness enhancement, or the like. Light transmissionmodule 340 can further include an optional processor 346 and memory 348,although in some embodiments these computing resources can beincorporated into ranging system controller 350. In some embodiments, apulse coding technique can be used, e.g., Barker codes and the like. Insuch cases, memory 348 can store pulse-codes that indicate when lightshould be transmitted. In one embodiment the pulse-codes are stored as asequence of integers stored in memory.

Light sensing module 330 can include a sensor array 332 and a receiver(Rx) optical system 334. Sensor array 332 can be a one-dimensional ortwo-dimensional array of photosensors. In some embodiments, eachphotosensor can include a collection of binary photon detectors (e.g.,SPADs or the like), while in other embodiments each photosensor can be alinear photodetector (e.g., an APD). Receiver optical system 334 andsensor array 332 taken together can form an array of micro-opticreceiver channels behind a bulk imaging optic as described in moredetail below. Each micro-optic receiver channel measures light thatcorresponds to an image pixel in a distinct field of view of thesurrounding volume. Each photosensor (e.g., a collection of SPADs) ofsensor array 332 can correspond to a particular emitter of emitter array342 as a result of a geometrical configuration of light sensing module330 and light transmission module 340. In an alternative embodiment,each sensor of sensor array 332 can correspond to multiple emitters(e.g., a cluster of VCSELs) of emitter array 342. In yet anotherembodiment, a single large emitter (e.g., a laser diode bar) could inemitter array 342 could correspond to multiple sensors within sensorarray 336.

In some embodiments, sensor array 332 of light sensing module 330 can befabricated as part of a monolithic device on a single substrate using,for example, CMOS technology, that includes both an array ofphotosensors, a processor 336 and a memory 338 for signal processing theraw signals from the individual photosensors (or groups of photosensors)in the array. The monolithic structure including sensor array 332,processor 336, and memory 338 can be fabricated as a dedicated ASIC. Insome embodiments, micro-optical components that are part of receiveroptical system 334 can also be a part of the monolithic structure inwhich sensor array 332, processor 334, and memory 338 are a part. Insuch instances, the micro-optical components can be formed on the ASICso that they become part of the monolithic structure with separatesubstrate layers for each layer of the receiver channel. For example, anaperture layer, a collimating lens layer, an optical filter layer and aphotodetector layer can be stacked and bonded to multiple ASICs at thewafer level before dicing. The aperture layer can be formed by laying anon-transparent substrate on top of a transparent substrate or bycoating a transparent substrate with an opaque film. In such anembodiment, the dicing step forms multiple ASICs, each with its ownmicro-optic structure bonded directly thereto. As another example, themicro-optical components can be formed as a separate monolithicstructure that can be bonded directly to an ASIC after the ASIC isseparated from a larger wafer via a dicing process. In this manner, theASIC and micro-optic structure can be bonded together to form a singlemonolithic structure. Yet other embodiments one or more components ofthe Rx module 330 may be external to the monolithic structure. Forexample, the aperture layer may be implemented as a separate metal sheetwith pin-holes.

As mentioned above, processor 336 and memory 338 (e.g., SRAM) canperform the signal processing. As an example of signal processing, foreach photosensor or grouping of photosensors, memory 338 of lightsensing module 330 can accumulate counts of detected photons oversuccessive time bins and these time bins taken together can be used torecreate a time series of the reflected light pulse (i.e., a count ofphotons vs. time). This time-series of aggregated photon counts isreferred to herein as an intensity histogram (or just histogram). Inaddition, processor 336 can accomplish certain signal processingtechniques, such as matched filtering, to help recover a photon timeseries that is less susceptible to pulse shape distortion that can occurdue to SPAD saturation and quenching. In some embodiments, one or morecomponents of ranging system controller 350 can also be integrated intothe same ASIC as sensor array 332, processor 336 and memory 338, therebyeliminating the need for separate a ranging controller module.

In some embodiments, the output from processor 336 is sent to rangingsystem controller 350 for further processing. For example, the data canbe encoded by one or more encoders of ranging system controller 350 andthen sent as data packets via the optical downlink to lower circuitboard assembly 360. Ranging system controller 350 can be realized inmultiple ways including, e.g., by using a programmable logic device suchan FPGA, as an ASIC or part of an ASIC, using a processor 352 with amemory 354, and some combination of the above. Ranging system controller350 can cooperate with base controller 366 or operate independently ofthe base controller (via pre-programed instructions) to control lightsensing module 330 by sending commands that include start and stop lightdetection and adjust photo-detector parameters. Similarly, rangingsystem controller 350 can control the light transmission module 340 bysending commands, or relaying commands from the base controller 366,that include start and stop light emission controls and controls thatcan adjust other light-emitter parameters such as, emitter temperaturecontrol (for wavelength tuning), emitter drive power and/or voltage.

If emitter array 342 has multiple independent drive circuits, then therecan be multiple on/off signals that can be properly sequenced by rangingsystem controller 350. Likewise, if the emitter array includes multipletemperature control circuits to tune different emitters in the arraydifferently, the transmitter parameters can include multiple temperaturecontrol signals. In some embodiments, ranging system controller 350 hasone or more wired interfaces or connectors (e.g., traces on a circuitboard) for exchanging data with light sensing module 330 and with lighttransmission module 340. In other embodiments, ranging system controller320 communicates with the light sensing module 330 and lighttransmission module 340 over a wireless interconnect such as an opticalcommunication link.

III. Light Transmission and Detection

FIGS. 4A and 4B depict an illustrative example of the light transmissionand detection process for a light ranging system according to someembodiments, with a focus on the emitter array and sensor array thatform an arrangement of emitter-sensor channels, as introduced above inreference to FIG. 2. FIG. 4A depicts a light ranging system 400 (e.g.,solid state or and/or scanning) collecting three-dimensional distancedata of a volume or scene 450 external to light ranging system 400. FIG.4B is an enlarged view of light ranging system 400 from FIG. 4A. Lightranging system 400 can be representative of any of light ranging systems200, 220 or 300 discussed above, as well as the various light rangingdevices discussed below. FIGS. 4A and 4B are highly simplified drawingsto highlight relationships between emitters and sensors, and thus othercomponents are not shown.

As shown in FIGS. 4A and 4B, light ranging system 400 includes a lightemitter array 410 and a light sensor array 420. Light emitter array 410includes an array of light emitters (e.g., an array of VCELs or thelike) that includes individual emitters, such as emitter 410(1) andemitter 410(9). Light sensor array 420 includes an array of photosensorsthat includes individual photo sensors, such as sensors 420(1) and420(9). The photosensors can be pixelated light sensors that employ, foreach pixel, a set of discrete photodetectors such as single photonavalanche diodes (SPADs) or the like. However, various embodiments candeploy other types of photosensors. In some embodiments, light rangingsystem 400 includes one or more sets of bulk optical elements (notshown), referred to herein as bulk optics, placed in front of lightemitter array 410 and/or the light sensor array 420 for redirecting thebeams in the directions shown.

Each emitter can be slightly offset from its neighbor and can beconfigured to transmit light pulses into a different field of view fromits neighboring emitters, thereby illuminating a respective field ofview associated with only that emitter. For example, emitter 410(1)emits an illuminating beam 415(1) (formed from one or more light pulses)into the circular field of view 452 (the size of which is exaggeratedfor the sake of clarity). Likewise, emitter 410(9) emits an illuminatingbeam 415(9) (also called an emitter channel) into the circular field ofview 454. While not shown in FIGS. 4A and 4B to avoid complication, eachemitter emits a corresponding illuminating beam into its correspondingfield of view resulting in a 2D array of fields of view beingilluminated (twenty one distinct fields of view in this examplecorresponding to the twenty one emitters, arranged in a 3×7 array, oflight emitter array 410).

Each field of view that is illuminated by an emitter can be thought ofas a pixel or spot in the corresponding 3D image that is produced fromthe ranging data. Each emitter channel can be distinct to each emitterand can be non-overlapping with other emitter channels, i.e., there is aone-to-one mapping between the set of emitters and the set ofnon-overlapping fields of view. Thus, in the example of FIGS. 4A and 4B,the system can sample twenty one distinct points in the 3D space. Adenser sampling of points can be achieved by having a denser array ofemitters or by scanning the angular positions of the emitter beams overtime such that one emitter can sample several points in space.

Each sensor can be slightly offset from its neighbor and, like theemitters described above, each sensor can see a different field of viewof the scene in front of the sensor. Furthermore, each sensor's field ofview substantially coincides with, e.g., overlaps with and is the samesize as a respective emitter channel's field of view. Similar to theemitters described above, the fields of view of the sensors can bescanned by rotation of the assembly. Scanning could also be accomplishedusing galvanometers, MEMS mirrors, or via some other method.

In FIGS. 4A and 4B, the distance between corresponding emitter-sensorchannels is exaggerated relative to the distance to objects in the fieldof view. In practice, the distance to the objects in the field of viewis much greater than the distance between corresponding emitter-sensorchannels and thus the path of light from the emitter to the object isapproximately parallel to the path of the reflected light back from theobject to the sensor (i.e., it is almost “back reflected”). Accordingly,there is a range of distances in front of the system 400 over which thefields of view of individual sensors and emitters are overlapped and itis over this range of distances that the system can most accuratelydetermine depth information.

Because the fields of view of the emitters are overlapped with thefields of view of their respective sensors, each sensor channel ideallycan detect the reflected illumination beam that originates from itsrespective emitter channel with ideally no cross-talk, i.e., noreflected light from other illuminating beams is detected. For example,emitter 410(1) emits an illuminating beam 415(1) into the circular fieldof view 452 and some of the illuminating beam reflects from the object460 as reflected beam 425(1). Ideally, reflected beam 425(1) is detectedby sensor 420(1) only. Thus, emitter 410(1) and sensor 420(1) share thesame field of view (i.e., field of view 452) and form an emitter-sensorpair. Likewise, emitter 410(9) and sensor 420(9) form an emitter-sensorpair, sharing field of view 454. In some embodiments emitter array 410and sensor array 420 are designed and configured (in conjunction withthe bulk optics) such that the fields of view of each emitter-sensorpair are non-overlapping (beyond a threshold distance) with the fieldsof view of other emitter-sensor pairs.

While the emitter-sensor pairs are shown in FIGS. 4A and 4B as being inthe same relative locations in their respective array, any emitter canbe paired with any sensor depending on the design of the optics used inthe system. In some embodiments, having identical bulk imaging optics infront of identically arranged emitter/sensor pairs can be advantageousfrom a design simplicity/cost perspective.

During a ranging measurement, the reflected light from the differentfields of view distributed around the volume surrounding the LIDARsystem is collected by the various sensors and processed, resulting inrange information for any objects in each respective field of view. Asdescribed above, a time-of-flight technique can be used in which thelight emitters emit precisely timed pulses, and the reflections of thepulses are detected by the respective sensors after some elapsed time.The elapsed time between emission and detection and the known speed oflight is then used to compute the distance to the reflecting surface. Insome embodiments, additional information can be obtained by the sensorto determine other properties of the reflecting surface in addition tothe range. For example, the Doppler shift of a pulse can be measured bythe sensor and used to compute the relative velocity between the sensorand the reflecting surface.

In some embodiments, the LIDAR system can be composed of a relativelylarge 2D array of emitter and sensor channels and operate as a solidstate LIDAR, i.e., it can obtain frames of range data without the needto scan the orientation of the emitters and/or sensors. In otherembodiments, the emitters and sensors can be scanned, e.g., rotatedabout an axis, to ensure that the fields of view of the sets of emittersand sensors sample a full 360 degree region (or some useful fraction ofthe 360 degree region) of the surrounding volume. The range datacollected from the scanning system, e.g., over some predefined timeperiod, can then be post-processed into one or more frames of data thatcan then be further processed into one or more depth images or 3D pointclouds. The depth images and/or 3D point clouds can be further processedinto map tiles for use in 3D mapping and navigation applications.

IV. LIDAR Unit with Integrated Architecture

FIGS. 5A-5B show a rotating LIDAR system 500 that employs a 360 scanningarchitecture, according to some embodiments of the disclosure. In someembodiments, LIDAR system 500 can spin in a clockwise orcounter-clockwise direction to observe the surrounding field around avehicle. System 500 can include a stationary base housing 502, anoptically transparent window 504, and a stationary lid 506 for providingprotection for the internal components of LIDAR system 500. Window 504can be made from a transparent material to allow for two-waytransmission of near IR light. Stationary base housing 502, window 504and lid 506 make up a water-resistant or waterproof system housing orenclosure 508 that fully encloses internal components of LIDAR system500 to protect the components from the elements. Housing/enclosure 508can be representative, for example, of housing 220 discussed above withrespect to FIG. 2A. In some embodiments, the enclosure can have agenerally cylindrical shape as shown in FIG. 5A.

In some embodiments, window 504 can extend fully around a periphery ofenclosure 508 and be attached to base housing 502 and lid 506 in a fixedrelationship. In such embodiments, a light ranging device 510 (shown inFIG. 5B), can rotate within enclosure 508 behind window 504. In otherembodiments, window 504 can rotate with light ranging device 510. Theconfiguration of base housing 502, window 504 and stationary lid 506shown in FIG. 5A is just one example of an enclosure 508 according toembodiments of the disclosure. A person of skill in the art willrecognize that other configurations of a suitable enclosure for LIDARsystem 500 are possible. As one example of a different configuration,lid 506 can be part of window 504. As another example, in embodimentswhere window 504 rotates with light ranging device 510, window 504 caninclude two or more separate windows separated by an opaque region. Forexample, in some embodiments, LIDAR system 500 can include a firstwindow aligned with an optical transmitter and a second window, spacedapart from the first window, aligned with an optical receiver. As usedherein, “aligned” means that the optical transmitter or receivertransmits or receives light through the window.

The internal components (not shown in FIG. 5A) of system 500 can includea rotary actuator and light ranging device, such as actuator 310 andlight ranging device 320 described with respect to FIG. 3. The lightranging device can be aligned with window 504 and can be spun by therotary actuator to project pulsed beams of light through window 504 intoa field surrounding LIDAR system 500 while the light ranging device isspinning continuously through 360 degrees in a clockwise orcounter-clockwise direction. Light reflected from the field back throughwindow 504 can then be detected by the light ranging device to determinedistance to objects in the field as described herein.

As described in more detail below, rotating LIDAR system 500 can employa highly integrated architecture and enables a highly compactconfiguration for the internal mechanical elements and circuitry.Accordingly, the overall form factor of LIDAR systems according to someembodiments of the disclosure can be smaller than many existing systems,for example, with an overall volume that is similar to or smaller thanthat of a coffee mug 550 as can be seen in FIG. 5A.

FIG. 5B shows an embodiment of LIDAR system 500 with the outerenclosure/system housing 508 (including window 504 and lid 506) removedto highlight the integrated, stacked-board design according to someembodiments of the disclosure. As shown in FIG. 5B, rotating LIDARsystem 500 includes a light ranging device 510 that includes an opticaltransmitter 512 and an optical receiver 514 mounted within a housing 515that includes a first housing portion 516 for the optical transmitterand a second housing portion 518 for the optical receiver. Light rangingdevice 510 is mechanically connected in a fixed relationship to aprinted circuit board 522 that forms the rotating end of stacked boardrotary actuator 520. The fixed side of stacked board rotary actuator520, including printed circuit board 524, is attached to base portion502 of the enclosure.

As described in more detail below, embodiments of the LIDAR systempossess a highly integrated design that makes them especially suitablefor a highly compact rotating LIDAR system. The various functionalelements of the LIDAR system (both mechanical and electronic) areintegrated into a stacked circuit board assembly that includes the oneor more circuit boards stacked in a parallel arrangement, as shown inFIG. 5B, e.g., circuit boards 522, 524, 526 and 528. In someembodiments, the power system, electric motor, communication system, andLIDAR control system are all integrated into the one or more stackedplanar circuit boards of the stacked board rotary actuator 520. Lightranging device 510 can be conveniently attached to the top board 522 byway of one or more multi-pin connectors or the like (not shown). As willbe detailed below, the boards can include a central aperture throughwhich a central shaft passes. The upper boards can be attached to theupper portion of the shaft via one or more bearings. Each of the boardscan be arranged with its planar surface perpendicular to the shaft andtherefore the axis of rotation. As a result of this configuration,assembly and maintenance are much simpler relative to other systems thatemploy multiple boards in different orientations within the LIDARsystem.

FIGS. 6A-6C show cross-sectional views of LIDAR systems 600, 650 and 660in accordance with various embodiments of the disclosure. Morespecifically, the individual components shown in FIGS. 6A-6C correspondgenerally to those already described above in reference to FIG. 3, withthe views shown FIGS. 6A-6C providing examples of the geometricplacement of the various circuit elements according to differentembodiments. FIGS. 6A and 6B each show embodiments that employ opticalcommunication between the upper and lower circuit board assemblies whileFIG. 6C shows an embodiment that employs inductive communication betweenthe upper and lower circuit board assemblies. FIGS. 6D-6E provide viewsof surfaces of the individual circuit boards according to someembodiments to further illustrate the concentric circumferentialarrangement of a number of individual circuit elements.

Referring now to FIG. 6A, LIDAR system 600, which can be representativeof LIDAR system 500, can include a light ranging device 602 along withupper and lower circuit board assemblies 610 and 620, respectively, inwhich upper board assembly 610 rotates with respect to lower boardassembly 620 around an axis 605 that is perpendicular to the boardassemblies. Circuit board assemblies 610 and 620 are each structuralcomponents of LIDAR system 600 that holding all or essentially all ofthe components of the LIDAR system. The two piece design enables system600 to have reduced size and increased reliability compared to manycurrently available LIDAR systems and enables system 600 to bemanufactured at a reduced cost.

Light ranging device 602 can be mounted to one of the circuit boards inupper board assembly 610 enabling the light ranging device to rotatewith upper board assembly 610 while lower board assembly 620 can bemounted to base 604 and or sidewall 606, each of which is a part of thestationary base of LIDAR system 600. Rotation of upper circuit boardassembly 610 and light ranging device 602 is enabled by a bearing system607 located on a hollow shaft 606 centered along the longitudinal axisor rotation 605.

Each of the assemblies 610, 620 can include two or more stacked planarcircuit boards arranged in a parallel relationship with each other. Inthe specific embodiment shown, upper assembly 610 includes a rotorcommunication board 612 and a rotor control board 614 while lowerassembly 620 includes a stator communication board 622 and a statorcontrol board 624. An electric motor can be integrated directly on theboard assemblies, along with an encoder, a wireless power system andoptical communication system as described in more detail below. Many orall of these same elements are also integrated on the board assembliesof LIDAR systems 650 and 660 shown in FIGS. 6B and 6C, respectively.Thus, to simplify the description of the FIGS. 6A-6C and avoidrepetition, like reference numbers are used to indicate like elementsand the description of such like elements is typically not repeated.

The highly integrated, stacked board design of LIDAR system 600 providesfor a system that has a greatly simplified assembly process incomparison to systems that employ numerous stand-alone modules for eachof the different functional elements of a LIDAR system. In alternativeembodiments, LIDAR systems of the present disclosure can include upperand lower board assemblies that are each a single circuit board evenfurther simplifying the stacked board design. For example, LIDAR system650 shown in FIG. 6B includes a single lower circuit board 652 and asingle upper circuit board 654.

While not shown explicitly in FIGS. 6A-6C, one or more supporting powercircuits, drive/control circuits, and communication circuits can bepaired with each of the systems discussed below and these supportingsystems can also be integrated onto one or more circuit boards of therotary actuator. For example, a motor driver for providing a three-phasedrive current to the solenoids of the stator can be attached to asurface of a circuit board of the lower circuit board assembly 620.Power drive and conditioning circuits can be paired with the wirelesspower transmission components and mounted to the upper and/or lowerboard assemblies. Supporting circuitry for the digital communicationsystem, such as buffers, LED/laser current drivers, encoders/decoders,clock recovery circuits, photodetector drive and conditioning circuits,etc., can also be mounted to one or more boards of the circuit boardassemblies. Some of these elements will be discussed in further detailbelow but one or ordinary skill in the art will appreciate that anynumber of arrangements and configurations of standard circuit componentscan be employed without departing from the scope of the presentdisclosure. In some embodiments, because of the nature of therotationally symmetric optical uplink, wireless power rotarytransformer, brushless dc motor, and rotary encoder, any concentricordering of these subsystems about the shaft can be employed.

V. Optical Links

1.Integrated Central Optical Downlink

In some embodiments, hollow shaft 606 can serve not only as a centralstructural member that supports each of the board assemblies, but alsoserves as a housing for a downlink optical communications channel (“thedownlink channel”) for providing data, e.g., ranging and/or operationaldata, from the turret assembly to the control and processing circuitrylocated in the lower circuit board assembly 620 (also referred to as thebase system). The optical downlink channel can include an opticaldownlink transmitter 626 and an optical downlink receiver 628 each ofwhich can be centered along rotational axis 605. Optical downlinktransmitter 626 can be attached (e.g., soldered) directly to a surfaceof a circuit board of upper circuit board assembly 610 and can bepositioned such that it can transmit optical signals through a centralhole or opening in the hollow shaft 606. Likewise, the optical downlinkreceiver 628 can be attached (e.g., soldered) directly to a surface of acircuit board of the lower circuit board assembly 620. The opticaldownlink receiver 628 can be positioned on the lower end of the shaftand aligned with the optical downlink transmitter 626 such that it isable to receive optical signals transmitted from the optical downlinktransmitter 626.

The optical transmitters and receivers used for the optical downlink ofthe rotary actuator can be any suitable optical emitter or detector. Forexample IR LEDs, laser diodes, VCSELs, and the like can be used for theoptical emitters. Likewise any suitable light detection technology canbe used for the receivers, such as, photodiodes or the like.

2.Integrated Optical Uplink

An optical uplink channel can be formed between a circumferentialarrangement of multiple optical uplink transmitters 642 and acomplementary circumferential arrangement of multiple optical uplinkreceivers 632. As with the optical downlink transmitter/receiver pair,the individual optical uplink transmitters and optical uplink receiverscan be directly attached (e.g., soldered) to respective circuit boardsof the lower and upper circuit board assemblies, respectively. Opticalcommunication components that are disposed on the lower circuit boardassembly are also referred to herein as “base optical communicationcomponents”. Optical communication components that are disposed on theupper circuit board assembly, or turret, are also referred to herein as“turret optical communication components.” Advantageously, the wall ofthe hollow shaft 606 provides for optical isolation between the uplinkand downlink channels and therefore minimizes crosstalk.

The individual emitter and receivers of the circumferential arrangementscan be coupled together to act together as a single composite receiverand a single composite transmitter. For example, as the system rotates,the overall optical intensity of the uplink signal detected by the fullarrangement of optical uplink receivers varies only slightly as theindividual emitters/detectors pass each other. Furthermore, the numberof individual transmitters in the composite transmitter can be the sameas or different from the number of individual receivers in the compositereceiver.

The optical transmitters and receivers used for the optical uplink ofthe rotary actuator can be any suitable type of optical emitter ordetector. For example, a ring of IR LEDs, laser diodes, VCSELs, or thelike can be used as the composite optical transmitter. Likewise anysuitable type of light detection technology can be used for thereceivers, e.g., a ring of photodiodes or the like can be used as thecomposite optical receiver. In addition, the optical transmitters andreceivers used for the optical uplink can be the same or different type(e.g., power and wavelength) as those used for the downlink.

An example of a circumferential arrangement of optical uplinktransmitters 642 is shown in FIG. 6D, which illustrates a top view of astationary circuit board (e.g., circuit board 622 of FIG. 6A). In thisexample, there are six (6) optical uplink transmitters 642 that arecircumferentially arranged around the central hole 672. The six (6)transmitters are evenly spaced around the circle 674 whose center islocated at the center of the shaft (and thus the center of hole 672) andtherefore overlapped with the axis of rotation.

The opposing surface of the rotating circuit board (e.g., circuit board612 of FIG. 6A or circuit board 654 of FIG. 6B) includes a correspondingcircumferential arrangement of optical uplink receivers 632, as shown inFIG. 6E, which illustrates a bottom view of a rotating circuit boardaccording to some embodiments. In this example, there are seven (7)optical uplink receivers that are circumferentially arranged around thecentral hole 672. The seven (7) receivers are evenly spaced around thecircle 684 whose center is located at center of the shaft and thereforeoverlapped with the axis of rotation. Accordingly, as the board rotates,the arrangement of optical uplink receivers 632 rotates about the axisof rotation. Because the radius of circle 684 is same as the radius ofcircle 674, the transmitters are aligned with the receivers and therotation merely results in a slight rise and fall of the average signalover time with a frequency being a multiple of the rotation frequency ofthe turret system. The number of transmitters needed for a reliableuplink channel depends on both the nominal power of the transmitters aswell as the divergence of the light cone that is emitted from eachtransmitter. Ideally, the spot size of the transmitter light at thefront surface of the rotating board is large enough that the individualspots overlap to such an extent that as the rotating board rotates, theoverall variation in the average intensity seen by the collection ofreceivers is below a specified value.

While FIGS. 6D and 6E depict an embodiment in which an optical downlinkchannel is formed within hollow shaft 606 and an optical uplink channelis formed between a circumferential arrangement of multiple opticaluplink transmitters and a complementary circumferential arrangement ofmultiple optical uplink receivers disposed outside the shaft, in otherembodiments other arrangements of optical channels are possible. Forexample, in some embodiments an uplink channel can be formed withinhollow shaft 606 and a downlink channel can be formed outside the shaft.In still other arrangements both a downlink and an uplink channel can beformed inside shaft 606 (e.g., using separate light guides) or both adownlink channel and an uplink channel can be formed outside the shaftin separate circumferential arrangements of optical components.

VI. Inductive Communication Links

Referring back to FIG. 6C, FIG. 6C shows an embodiment that employs aninductive communications system 666, 668 between the upper and lowercircuit board assemblies. In this example, data uplink and downlink areprovided by pairs of coils 666 a-e and 668 a-e respectively mounted onthe lower circuit board assembly and upper circuit board assembly, asshown. The coils can include both data lines and clock lines. Each coilcan be embedded within a separate channel, e.g., a circular channel, ofa housing, such as upper coil housing 666 and lower coil housing 668that are themselves mounted to the surfaces of their respective circuitboards. In some embodiments, there can be several coils that are usedfor multiple inductive data lines, e.g., downlink channel 1 transmittercoil 666 b and downlink channel 1 receiver coil 668 b, downlink channel2 transmitter coil 666 c and downlink channel 2 receiver coil 668 c. Insome embodiments, the downlink clock signal can be transmitted via aseparate coil pair, e.g., downlink clock transmit coil 666 a anddownlink clock receiver coil 668 a. Likewise, data uplink channels canbe formed from one or more pairs of coils, e.g., by uplink transmittercoil 668 d and uplink receiver could 666 d. Like the downlink, the datauplink clock signal can also have a dedicated channel formed from a pairof coils, e.g., uplink clock transmitter coil 668 e and uplink clockreceiver coil 666 e.

In some embodiments, the use of an inductive communications links canprovide a number of advantages over an optical configuration, including:(1) replacement of the hollow shaft 606 with a solid shaft 665 which issimpler and easier to construct; (2) in some situations, an inductivecoil arrangement can require less stringent tolerances on mechanicalalignment and thus have lower cost of manufacture; (3) an easierarrangement for passing multiple channels of information between theboards; (4) can enable passing a clock along with data, which removesthe need for clock and data recovery (CDR) chips; (5) can allow forscaling bandwidth by providing a multichannel (parallel) datatransmission lines arrangement; and (6) by distributing a separate clocksignal between the boards, deterministic timing behavior can be achievedbetween the lower board assembly (stator) and upper board assembly/lightranging unit (rotor).

While FIG. 6C shows an embodiment with five coil pairs, any number ofcoil pairs can be implemented without departing from the scope of thepresent disclosure. For example, a two coil pair configuration havingonly one data uplink channel and one downlink channel can beimplemented. In this case, the clock signal can be provided via theuplink channel and the downlink clock can be derived from this uplinkclock signal. In other embodiments, three coil pairs can be employed,one for uplink data, one for downlink data and one for the uplink clocksignal, again, with the downlink clock signal being derived from theuplink clock signal. Four coil pair configurations are also possiblethat provide for both uplink and downlink clock signal channels. Inaddition to all the above, any number of data cannels can be employedwithout departing from the scope of the present disclosure.

VII. Integrated Electric Motor

According to certain embodiments, an electric rotary motor can beintegrated directly onto the circuit boards. The motor can have a“pancake” or “axial” design having a planar rotor assembly on a rotorboard that opposes a planar stator assembly on an opposing stator board.The stator and rotor assemblies of the electric motor can be integratedonto the boards of the rotary actuator 608, i.e., the elements of theelectric motor are one of many components on the surface of the printedcircuit boards and thus a separate motor module is not required forLIDAR system 600. For example, referring back to FIG. 6D, statorassembly 644 can include an annular arrangement of multiple statorelements 644(i), e.g., vertically oriented solenoids (having theirlongitudinal axes perpendicular to the surface of the board) that areaffixed (e.g., using an adhesive) to a board of the lower circuit boardassembly 620 (e.g., board 622) or to a soft magnetic core that is thenaffixed to the lower circuit board assembly 620. Examples of the statorelements are shown in the top view of FIG. 6D. Each stator element644(i) can include a solenoid coil 644 a wound around a core 644 b ofmagnetic material, e.g., ferrite or the like. The coils are orientedsuch that the magnetic field exiting the solenoid is substantiallyoriented in a direction that is substantially perpendicular to the planeof the circuit board. In the embodiment shown in FIG. 6D, statorassembly 644 includes eighteen (18) individual stator elements 644(i)evenly spaced apart from each other, but embodiments of the disclosureare not limited to a stator assembly with any particular number ofstator elements and other embodiments can include fewer or moreindividual stator elements 644(i). For example, in some embodimentsstator assembly 644 includes at least 12 individual stator elements644(i) in an annular arrangement. Also, in some embodiments, the numberof individual stator elements 644(i) in stator assembly 644 is amultiple of three and a motor driver circuit and controller (not shownin FIG. 6D) provide a three-phase alternating signal to stator assembly644 to control the rotation rate of board 622 and thus the rotation rateof light ranging device 602.

Positioned directly opposite the motor stator assembly 644 and attachedto a board of the upper circuit board assembly 610 is the motor rotorassembly 634. In some embodiments, motor rotor assembly 634 can be apassive element that includes an annular arrangement of permanentmagnets 634(i), with their poles arranged in an alternating pattern tosequentially oppose and attract the opening of the various solenoidcoils of the stator assembly, as shown in more detail in board viewshown in FIG. 6E. Thus, as shown in FIG. 6E, each individual magnet 634a can have its poles arranged opposite to its adjacent magnets 634 b,and each individual magnet 634 b can have its poles arranged opposite toits adjacent magnets 634 a. Additionally, while the embodiment of thestator assembly 644 shown in FIG. 6E includes twenty four (24)individual magnets 634(i) evenly spaced apart from each other,embodiments of the disclosure are not limited to a rotor assembly withany particular number of elements and other embodiments can includefewer or more individual magnets 634(i). Further, as can be seen in FIG.6D and 6E, the motor stator assembly 644 and the motor rotor assembly634 can have an overall circular ring shape with both stator and rotorcircles having the same radius and center positions (e.g., both ringscan be centered on the shaft).

While the embodiments shown in FIGS. 6D and 6E employ rotor elementsthat are permanent magnets and stator elements that are solenoid coils,the opposite configuration can also be employed without departing fromthe scope of the present disclosure. For example, solenoids can beemployed as the rotor elements and permanent magnets can be employed asthe stator elements, in which case, power to the stator elements can beprovided by the wireless power transmission system described below. Inaddition, rather than employing permanent magnets as rotor/statorelements, electromagnets can be employed in certain embodiments. One ofordinary skill having the benefit of this disclosure will appreciatethat any implementation of a PCB mounted brushless DC motor can beemployed, for example, any non-contact configuration of solenoid coilsand permanent magnet elements can be employed and any drive scheme thatimplements rotary motion of the underlying hardware can be employedwithout departing from the scope of the present disclosure.

VIII. Integrated Wireless Power Transmission System

To provide power to the circuit elements connected to the rotating uppercircuit board assembly 610, the rotary actuator 608 includes a wirelesspower system, also referred to herein as a rotary transformer. Thewireless power system includes a wireless power transmission subsystemincluding a wireless power transmitter 648 and a wireless powerreceiving subsystem including a wireless power receiver 638. Thewireless power transmitter 648 can be a transmitter coil in the form ofa circular loop antenna (e.g., a single turn or multi-turn coil) that isattached to a surface of a circuit board of the lower circuit boardassembly 620 (e.g., board 622) as shown, for example, in FIG. 6D.Likewise, the wireless power receiver 638 can be a receiver coil in theform of a circular loop antenna (e.g., a single turn or multi-turn coil)that is attached to a surface of a circuit board of the upper circuitboard assembly 610 (e.g., board 612) as shown in FIG. 6E. The centers ofboth the wireless power transmitter 648 and the wireless power receiver638 are positioned at the center of the hollow shaft 606 and aretherefore concentric with, the optical encoder ring, the electric motorassemblies, and the optical uplink receiver/transmitters.Advantageously, the wireless power transmitter and receiver can bepositioned at the outermost region of the boards 622 and 612 to maximizethe area (and therefore inductance) of the circular loops whichmaximizes power transfer efficiency and advantageously blocks light fromthe environment or the internals of the LIDAR system from reaching theoptical encoder, uplink or downlink.

In some embodiments, the wireless power transmitter 648 and a wirelesspower receiver 638 can be placed within an annular region of theirrespective boards with the walls and bottom of the annular regionsformed from a magnetic material, e.g., ferrite or the like. For example,FIG. 6E shows wireless power receiver 638 disposed within an annularregion formed from ferrite walls 686 and 688 (not shown in FIGS. 6A-6C)and an occluded ferrite bottom. Such an arrangement of ferrite materialsis depicted in FIG. 6F, which is a simplified cross-sectional view of aportion of a multi-coil wireless power receiver 638 positioned within anannular channel defined by ferrite walls 686, 688 and a bottom ferritewall 690. The arrangement shown in FIG. 6F helps channel the magneticfields between the transmitter and receiver to improve power transferefficiency and reduce electromagnetic radiation leaking from the system.

IX. Integrated Optical Encoder

The rotary actuator 608 further includes an integrated optical encoderassembly that allows for readout of the angular position of the uppercircuit board assembly 610 relative to the lower circuit board assembly620. The optical encoder assembly includes a patterned annular opticalencoder 646 and rotary encoder detector 636 for reading off the angularposition of the assembly by, for example, detecting and counting thenumber of patterns that pass the rotary encoder detector 636 as thesystem rotates. In certain embodiments, rotary encoder detector 636 caninclude an illumination device, such as an LED and a detector, such as aphotodiode or imaging detector for illuminating and detecting thepatterned surface of the annular optical encoder. In some embodiments,the annular optical encoder can include a start code that occurs at aunique position on the annulus or provides absolute encoding patternsthereby enabling an absolute angular orientation measurement. In someembodiments, the encoder system is magnetic instead of optical in natureand relies on a similarly positioned magnetic encoder strip and magneticencoder reader.

In some embodiments, the annular optical encoder 646 can be attached toa surface of a circuit board of the lower circuit board assembly 620(e.g., board 622) and the rotary encoder detector 636 can be attached toa surface of the upper circuit board assembly 610 (e.g., board 612) asshown here, or vice versa. Regardless of which board it is placed on,the annular optical encoder 646 can be arranged to have its center atthe center of the hollow shaft 606 and is therefore concentric with boththe electric motor assemblies and the optical uplinkreceiver/transmitters as shown, for example, in FIG. 6D. In someembodiments, the rotary encoder detector 636 is positioned on therotating circuit board, anywhere above the annular optical encoder 646,e.g., as shown in FIG. 6E.

Advantageously, the encoder assembly can be positioned between thewireless power transmission system and the electric motor assembly tomaximize the optical isolation between the encoder detector and thetransmitters of the optical uplink system. As shown in the example ofFIG. 6A, in some embodiments the annular optical encoder 646 can be onthe stator side of the rotary actuator 606 while the rotary encoderdetector 636 on the rotor side. While this is a non-standardconfiguration for rotary actuators, this configuration is advantageousfor a LIDAR application. For example, by removing the rotary connectionbetween the rotary encoder detector 636 and the light ranging device 602in this manner, the implementation of a low latency connection betweenthe two systems can be implemented. In LIDAR applications a low latencyconnection can be important for quickly ingesting the angular positionmeasurements of the rotary encoder detector 636 and correlating thecurrent ranging information with the current angular position of therotor for increased spatial accuracy.

X. Method of Assembly

FIGS. 7-8 show exploded views of a LIDAR system to illustrate theassembly process according to certain embodiments. FIG. 7 illustratesthe mechanical assembly of the lower circuit board assembly (alsoreferred to herein as the base assembly). FIG. 8 illustrates themechanical assembly of the upper circuit board assembly and itsattachments to both the lower circuit board assembly and the lightranging device, thereby forming the full LIDAR system.

1. Assembling the Lower Circuit Board Assembly

FIG. 7 shows an exploded view of a lower circuit board assembly 700 toillustrate an assembly process of the compact LIDAR system according tocertain embodiments. In the embodiment shown in FIG. 7, lower circuitboard assembly 700 is of a two-board configuration, similar to thatdescribed above in reference to FIG. 6A. Specifically, lower circuitboard assembly 700 includes first and second sub-boards, referred toherein as the base control board 720 and the stator board 730. In someembodiments, base control board 720 and stator board 730 correspond toboards 643 and board 641, respectively, as shown in FIG. 6A.

The assembly of lower circuit board assembly 700 can begin with basecontrol board 720 being mechanically attached to a base housing unit 710by way of screws 728. As already described above in reference to FIGS. 3and 6A, the base control board can include a number of circuit elements,including a base controller, similar to base controller 366. Supportingcircuitry, e.g., drivers for, the elements of the optical communicationssystems, wireless power transmission system, and the rotary encodersystem can also be included on the base control board. To enable theoptical downlink communications channel, an optical downlink receiver722 can be mounted to (e.g., soldered to) an upper surface of basecontrol board 720 in a central region of the board as described above inreference to FIG. 6A.

In some embodiments (e.g., as described above in reference to FIG. 6B),optical downlink receiver 722 and the other supporting circuit elementsare integrated directly onto stator board 730 thereby eliminating theneed for a separate base control board 720. In such a case, assembly oflower circuit board assembly 700 can begin by attaching a heat spreadingelement 725 directly to the base 710 or in cases that do not employ thebase or heat spreading element 725, the assembly can begin by installingstator board 730.

After base control board 720 is attached to base 710, shaft 715 can beattached to base control board 720, using screws 706. In someembodiments, shaft 715 can be attached directly to base 710 for improvedthermal conduction of heat from the upper circuit board assembly to thebase 710 via the bearing system (shown in more detail in FIGS. 8A and 8Bbelow). As described above in reference to FIGS. 6A-6B, shaft 715 caninclude a central hole 716 through its length that provides an openoptical path for an optical downlink channel. As such, shaft 715 can beplaced directly on top of optical downlink receiver 722 locatedgenerally near the center of base 710. In some embodiments, regardlessof the shape of the outer circumference of base control board 712 orbase 710, shaft 715 defines the axis of rotation 705 of the system.Thus, the position of shaft 715 need not be directly in the center ofbase control board 720 or in the center of base 710.

After shaft 715 is attached to base control board 710, heat spreadingelement 725 can be attached to base control board 720 by one or morescrews 716. In some embodiments, heat spreading element 725 can be madefrom a material having a high thermal conductivity (e.g., aluminum andthe like). In addition, there may be one or more intervening thermalfoam pads between heat spreading element 725 and the boards to preventelectrical shorts while providing a conductive heat path. In someembodiments, heat spreading element 725 makes thermal contact with oneor more portions of the lower surface of stator board 730 and one ormore portions of the upper surface of base control board 720 therebyproviding a thermal path for concentrated heat from the circuit elementsof these boards to more evenly distribute amongst the boards. On itsperiphery, heat spreading element 725 may also make thermal contact withthe sides of base 710 and thus provide an improved thermal path for heatto be conducted from the boards to base 710 and eventually out of thesystem.

After securing heat spreading element 725, stator board 730 can beattached by way of screws 736. In some embodiments, stator board 730 canbe electrically connected to base control board 720 by way of one ormore multi-pin electrical connectors (e.g., lower connectors 724 and726). In some embodiments, the physical connection between the boards ismade by applying a mechanical connection pressure between stator board730 and base control board 720 (e.g., by pressing the stator board ontothe base control board after it has been attached to base 710). Theconnection pressure can be maintained over the life of the system byscrews 736 used to secure stator board 730 to base control board 720.

Once assembled and secured to the base 710, one or more optional colorcameras 732 can be positioned around the periphery of stator board 730to have a clear visual path out of base 710 through one or more imagingapertures 712, which in some embodiments can be clear apertures or cancontain one or more optical elements to assist with imaging. In otherembodiments, the color cameras 732 can be mounted directly to base 710rather than be mounted to stator board 730. Color cameras 732 enableLIDAR data that is accumulated by the LIDAR system to be supplemented bycolor imaging data such as still frames and/or video as described inU.S. application Ser. No. 15/980,509 entitled “Augmenting PanoramicLIDAR Results with Color,” which is incorporated herein by reference inits entirety for all purposes.

2. Assembling the Upper Circuit Board Assembly and Attaching to theLower Circuit Board Assembly

FIG. 8A is an exploded view of a compact LIDAR system 800 to illustratean assembly process of a LIDAR system according to some embodiments ofthe disclosure. LIDAR system 800 can be, for example, LIDAR system 500shown in FIG. 5A. LIDAR system 800 includes lower circuit board assembly700, described above with respect to FIG. 7, an upper circuit boardassembly 810, a light ranging device 820, and an enclosure 830. As shownin FIG. 8A, LIDAR system 800 includes an upper circuit board assembly 8that.

As shown in FIG. 8A, upper circuit board assembly 810 is of a two-boardconfiguration, similar to that described above in reference to FIG. 6Aand includes a ranging device control board 840 and the rotor board 850.In some embodiments, ranging device control board 850 and rotor board730 correspond to stator control board 624 and rotor control board 614,respectively described above in reference to FIG. 6A.

Rotor board 850 includes a bearing assembly 860, shown in FIG. 8B, whichis an exploded view of rotor board 850. Bearing assembly 860 includesbearings 862 and 864, which are inserted into either end of a t-shapedbearing housing 865. T-shaped bearing housing 865 can then attached torotor board 850 with screws 866.

Rotor board 850 can be placed on top of assembled lower circuit boardassembly 700 by fitting the central portion of T-shaped bearing housing865 over shaft 715. A circular nut 852 can then be fitted into acircular central recess 854 in the top surface of the t-shaped bearinghousing 86 and threaded onto the top of shaft 715 to securely attachrotor board 850 to lower circuit board assembly 700. As discussed above,rotor board 850 is able to rotate relative to lower circuit boardassembly 700 due to the rotational coupling made between shaft 715 andbearings 862 and 864.

Ranging device control board 840 can then be joined to rotor board 850by applying a downward pressure to the ranging device control board 840.To provide an electrical connection between ranging device control board840 and rotor board 850, one or more electrical connectors can beattached to (e.g., soldered to) the lower surface of ranging devicecontrol board 840 (not visible in FIG. 8A) and the upper surface ofrotor board 850 (e.g., connector 856). Ranging device control board 840can then be secured to rotor board 850 using screws 846.

3. Attaching the Laser Ranging Device to the Rotary Actuator

Once the upper circuit board assembly has been assembled and secured tothe lower circuit board assembly, light ranging device 820 can beelectrically connected to the upper surface of ranging device controlboard 840, which mechanically connects the light ranging device toT-shape bearing housing 865. Light ranging device 820 includes a Txmodule 822 and a Rx module 824 each of which can have dedicatedelectrical connectors that mate with corresponding connectors 844 and846 disposed on the upper surface of light ranging device control board840. As with the other boards in the system, connecting the lightranging device 820 to the rest of the assembled system can be achievedby applying a pressing force to the components. Once the connections aremade, the pressing force can be maintained by screws 826 mounted oneither side of light ranging device 820 as shown. In addition, au-shaped bracket 828 can secured to light ranging device 820 withadditional screws 826 to provide further structure to the assembly.

Once all the internal components are assembled, enclosure 830 can bedropped over the entire assembly and affixed to base 700, e.g., usingone or more screws as well as adhesive, if required to achieve a morerobust seal. Enclosure 830 can include an optically transparent windowas described above with respect to FIG. 5 that enables laser pulses fromTx module 822 to be projected from the LIDAR system into the surroundingenvironment and enables reflected and scattered light from the pulses tobe received by the LIDAR system via Rx module 824.

In the assembly process described above, various arrangements of screwsand brackets are disclosed merely for the sake of example. Embodimentsof the compact LIDAR system are not required to employ screwarrangements that are identical to that shown in FIGS. 7-8 and anynumber, arrangement, and type of fastener, including adhesive,deformable pins or latches, rivets, or welds, can be used withoutdeparting from the scope of the present disclosure.

XI. Optics and Optoelectronics

FIGS. 9A-9C show a perspective view, a front view, and a zoomed frontview, respectively, of a light ranging device 900 according to certainembodiments. The light ranging device 900 can correspond to embodimentsdescribed above in reference to FIGS. 1-6, e.g., light ranging device320 described above in reference to FIG. 3 or light ranging device 510described with respect to FIG. 5. Light ranging device 900 includes twomain modules: a light transmission (Tx) module 910 and a light sensing(Rx) module 920 spaced apart from each other within a common housing ormount 905 that includes two lens tubes, e.g., transmitter lens tube 912and detector lens tube 922. The light Tx module and light Rx moduleseach include bulk optics modules (not shown) that are positioned infront of their respective sensors/emitters, e.g., by sliding the bulkoptics module into the appropriate lens tube. The bulk optics modulesare described in more detail below. On the transmission side, locatedbehind the Tx-side bulk optics module is, optionally, a Tx-sidemicro-optics assembly. Details of the micro-optics assembly are setforth below in reference to FIGS. 10-11. Behind the optionaltransmit-side micro-optics assembly is an emitter array 914, e.g., amonolithic single-chip NIR VSCEL array fabricated on InGaAs, or thelike. On the detector side, located behind the Rx-side bulk opticsmodule is a Rx-side micro-optics assembly, also described in more detailbelow in reference to FIGS. 10-11. Behind the Rx-side micro-opticsassembly is a single chip detector array and ASIC combination 924, e.g.,a monolithic single-chip MR SPAD array fabricated on a CMOS process, orthe like.

Both Rx module 920 and Tx module 910 are backed by circuit boards 926and 916, respectively, that include additional supporting circuitry forthe light ranging device, e.g., voltage regulators, VCSEL currentdrivers, and the like. For example, circuit board 926 can includecircuitry for counting signals from SPADs to include in a histogram oftime bins, which may be specified by a time-to-digital converter.Circuit board 926 can also include match filtering for analyzing thehistogram to determine a received time. In some embodiments, aprogrammable computation element such as an FPGA (e.g., to performadvanced filtering, such as interpolation) may be operatively connectedto the Rx module 920.

While not shown in FIG. 9A-9B, the FPGA can be located on one or moreboards of the upper board assembly of the rotary actuator describedabove, that include, e.g., the rotor half of a brushless motor, thereceive side of a rotary transformer power link, the receive side of arotary optical uplink, and the transmit side of a rotary opticaldownlink. These elements taken together are referred to herein as theturret assembly of the LIDAR system. In certain embodiments, the turretassembly can spin at a frequency of 1 Hz to 30 Hz, taking rangemeasurements at fixed angular intervals. In one embodiment, for anygiven full rotation (“frame”), a 64×2048 resolution depth image can beproduced, although the user may select other resolutions by changingdevice operating parameters. In some embodiments, the LIDAR system canacquire 2,621,440 points (range measurements) per second.

1.Optical Systems for the Tx and Rx Modules

FIG. 10 shows an optical block diagram of a light ranging device 1000according to some embodiments of the disclosure. As shown in FIG. 10,light ranging device 1000 includes a light transmission (Tx) module 1010and a light sensing (Rx) module 1040. Light transmission module 1010 canbe representative of Tx module 910 while light sensing module 1040 canbe representative of Rx module 920. Embodiments of the disclosure arenot limited to the specific optical configurations shown in FIG. 10. Inother embodiments, light transmission module 1010 and light sensingmodule 1040 can include fewer, more or different optical components.Non-limiting examples of other configurations for light transmissionmodule 1010 and light sensing module 1040 are set forth in U.S.application Ser. No. 15/979,235 entitled “Optical Imaging Transmitterwith Brightness Enhancement,” filed on May 14, 2018, and U.S.Application No. 15/979,266 entitled “Spinning LIDAR Unit withMicro-optics Aligned behind Stationary Window,” filed on May 14, 2018,the disclosures of each of which are incorporated herein by reference intheir entirety for all purposes.

Embodiments of the light ranging device 1000 can be employed within thecompact LIDAR system disclosed herein as described above in referenceto, e.g., FIGS. 5A-5B. The Tx module 1010 provides active illuminationof objects in the area around the LIDAR system by, e.g., transmittingpulses of narrow band light, e.g., NIR light having a spectral width of,e.g., 2 nm, 1 nm, 0.5 nm, 0.25 nm or less, into one or more fields ofview, as shown in FIGS. 1A-1B and 4 above. The Rx module 1040 detectsreflected portions of the transmitted narrowband light that is reflectedby the objects in the scene.

As shown in FIG. 10, Tx module 1010 can include a TX-side micro-opticspackage 1020 and a bulk optical element 1030. The TX-side micro-opticspackage 1020 includes a plurality of light emitters 1022, and optionallyincludes a micro-lens layer 1024 and an aperture layer 1026. Emitters1022 can be arranged in a one or two-dimensional array of transmitterchannels, e.g., channel 1025 shown in the boxed region. Each one of thetransmitter channels has one or more light emitters 1022, e.g., NIRVCSELs or the like, capable of emitting narrowband light, andoptionally, a micro-lens from lens layer 1024 and an aperture fromaperture layer 1026.

Light emitted from each one of the transmitters diverges as itapproaches one of the micro-optics of the Tx-side micro-optic lens layer1024. Micro-lenses from micro-lens layer 1024 capture the diverginglight and refocus it to a focal plane that is coincident with aperturesin aperture layer 1026 that includes an array of apertures thatcorrespond in position to the array of micro-optics and the array ofemitters. Aperture array 1026 can reduce crosstalk in the system. Afterexiting the micro-lenses, the focused light again diverges in the formof cones that then encounter the Tx-side bulk imaging optics module1030. Details of the Tx-side bulk imaging optics module 1030 arediscussed in more detail below.

In some embodiments, the separation between the micro-lens layer 1024and the Tx-side bulk imaging optics module 1030 is equal to the sum oftheir focal lengths, such that light focused at the aperture array 1026appears as collimated light at the output of the Tx-side bulk imagingoptics module 1030 with each collimated bundle of rays exiting theTx-side bulk imaging optics module 1030 at a different angle.Accordingly, the light from each emitter is directed to a differentfield of view ahead of the device. In some embodiments, the Tx-side bulkimaging optic 1030 is telecentric on the VCSEL side of the lens, i.e.,in a ray diagram of the system, all the chief rays entering anywherewithin the aperture of the bulk imaging optic 1030 leave the lenstravelling parallel to each other and intersect the VCSEL (image) planeat an angle of incidence that is substantially perpendicular to theVCSEL (image) plane. In this configuration the VCSEL arrayadvantageously operates as a telecentric source, i.e., the opticscapture substantially all light produced by the emitter array, evenlight that is emitted from the emitters on the outer edges of the array.Without the telecentric design, light captured by the outer emitters maybe reduced, scattered or refracted in an undesirable manner because oftheir highly oblique angle of incidence.

The Rx module 1040 includes an Rx-side bulk imaging optics module 1060and an RX-side micro-optics package 1050. The RX-side micro-opticspackage 1050 has either a one or two-dimensional array arrangement thatmatches the TX-side micro-optics package 1020, with a micro-opticreceiver channel 1055 for each corresponding micro-optic transmitterchannel 1025. The RX-side micro-optics package 1050 includes an Rx-sideaperture array layer 1056, an Rx-side micro-optics lens layer 1054, anarrow band optical filter layer 1028 and a sensor array layer 1052. Theportions of the emitted light that reflect off of objects in the field,shown as light rays 1005, enter the Rx-side bulk imaging optics module1060 from multiple directions. The Rx-side bulk imaging optics module1060 focuses light rays at a plane that is coincident with the Rx-sideaperture array layer 1056. The focused light then is captured by themicro-lenses of the Rx-side micro-optics lens layer 1054 and directed toa sensor array layer 1052 in a collimated fashion (i.e. having adivergence half angle of less than ten degrees).

In some embodiments, the sensor array layer 1052 includes a 1-D or 2-Darray of light sensors or a one or two dimensional array of groups oflight sensors, e.g., SPADS and the like. In some embodiments, eachsensor or group of sensors in the array corresponds to an emitter in theemitter module and thus a “pixel” in the ranging data.

In some embodiments, to remove spurious background light, a narrow bandoptical filter layer 1028 can be disposed within the layered structure,e.g. between the micro-optics array and the sensor array layer 1052. Thepass band of the narrow band optical filter layer 1028 can be chosen tocorrespond with the center wavelength of the emitters and the width ofthe pass band can be wide enough to accommodate any variation in theoutput wavelength across the emitter array. In some embodiments, where avery narrow pass band is desired, a control system can stabilize thewavelength of the emitters individually or as a whole. In someembodiments, where a very narrow pass band is desired, the collimationangle of the light passing through filter layer 1028 must be tightlycontrolled so that no angle-of-incidence shifts occur (as is common inthin-film interference filters); the collimation angle is primarilycontrolled by the size of apertures in RX-side aperture array layer1056, the focal lengths of the lenses in RX-side micro-optic lens layer1054, the relative positioning between RX-side aperture array layer 1056and RX-side micro-optic lens layer 1054, and surface quality and formprecision of RX-side micro-optic lens layer 1054. In some embodimentsthe narrow band optical filter layer 1028 is continuous planar layeracross the entire array of sensors. In other embodiments, the narrowband optical filter layer 1028 can be fabricated as an array ofmicro-optical elements that correspond with the pixel geometry of thesensor array layer 1052.

As with the Tx side, the individual elements of the Rx module 1040 formmicro-optic receiver channels, e.g., receiver channel 1055. According tocertain embodiments, the array of micro-optics and receivers can have alayered monolithic structure. Each micro-optic receiver channel 1055measures light for a different pixel in the sensor array layer 1052,i.e., the optics of the Rx module 1040 serve to map bundles of parallelrays entering the module from different angles to differentcorresponding spatial positions on the sensor array layer 1052. In someembodiments, the bulk imaging optics module 1060 is telecentric on thedetector side of the system to avoid the non-idealities in the imageplane in a manner similar to the TX side, as described above.

In some embodiments, the micro-optic receiver channels as formed by thecooperation between the micro-optic lens layer 1054, narrow band opticalfilter layer 1028, and Rx-side aperture array layer 1056 provide forincreased isolation between different pixels on the sensor array layer.This is advantageous because in some situations, such as when theemitter light is reflected from a strong reflector in the field, such asa stop sign, the photon flux at the Rx side for each channel can besizable, making the system susceptible to cross talk and blooming (i.e.the incoming light from one channel may be so bright that it isdetectible by an adjacent channel). One solution to the booming problemis to employ a complex time multiplexing scheme such that only oneemitter-detector pair (or a carefully chosen group of emitter-detectorpairs) are triggered at any given time, therefore eliminating the riskof cross talk. Such an arrangement requires additional timingelectronics and multiplexing software and hardware which adds additionalcost and complexity to the system. In addition, time-multiplexing is aninefficient data collection method because each receiver emitter pairmust be sequentially activated in series thereby increasing the overallacquisition time of the array as a whole. Advantageously, the design ofthe Rx side micro-optics assembly reduces cross-talk to such an extentthat time multiplexing and sequential activation is not necessary, i.e.,all channels can be employed at the same time to collect data points inparallel, in a manner similar to a flash LIDAR system.

The design of the micro-optical systems for the Rx module 1040 and theTx module 1010 advantageously enable the conceptual LIDAR arrangementdescribed above in reference to FIG. 3 where each transmitter element ispaired with a sensor element such that the sensor element views lightonly from the field of view that the transmitter illuminates. This 1:1pairing of fields of view helps eliminates cross-talk in the detectorfrom adjacent or neighboring pixels. The additional micro-opticalaperture layer also helps to eliminate cross-talk. The narrow bandfilter layer helps to remove background light which may contribute tospurious signal detection, eventually leading to ranging errors.

2.Micro-Optics

FIG. 11A shows a simplified top view of a micro-optics package 1100according to certain embodiments. Micro-optics package 1100 can beapplied on either or both the transmitter or detector side of the lightranging device and includes a plurality of channels 1102. For example ifimplemented on the receiver side, each channel 1102 would correspond toa single micro optical receiver channel, such as channel 1055.Similarly, if implemented on the transmitter side, each channel 1102would correspond to a single transmitter channel, such as channel 1025.In the example shown in FIG. 11A, the micro-optical channels are laidout as an m×n staggered array, e.g., laid out in 16×4 array. As anexample, if FIG. 11A represents receiver channels, for a receiverchannel size of 0.500 mm (diameter) the layout illustrated can beimplemented in a chip of size 8.000 mm by 2.000 mm.

Other array patterns are possible without departing from the scope ofthe present disclosure. For example, rather than a staggered array, anyof the following shaped arrays can be employed: a square array, a 1-Dstraight line array (m×1), a warped linear (m×1) array, a warpedrectangular m×n array, or arrays having any arbitrary pattern. As usedherein the term “warped” refers to embodiments where the spacing betweenreceiver channels is uneven. For example, receiver channels near thecenter, are spaced closer together, while the exterior channels arespaced further apart. The warped layout has an advantage of being ableto allow for correction of the distortion curve of a lens (i.e. theangles between the receiver channel fields of view are evenly spaced inthe object space).

FIG. 11B shows a cross-section of a single micro-optic receiver channel1120 according to some embodiments that can be representative of, forexample, receiver channel 1055 shown in FIG. 10. Receiver channel 1120serves to accept an input cone of light containing a wide range ofwavelengths, filters out all but a narrow band of those wavelengthscentered at the operating wavelength, and allows a pixel (photosensor)1171 to detect only or substantially only photons within theaforementioned narrow band of wavelengths. Embodiments of the disclosureare not limited to any particular configuration for receiver channelsand channel 1120 is just one example of a receiver channel that can beimplemented as receiver channel 1055.

In some embodiments, the receiver channel 1132 includes an inputaperture layer 1140 including an optically-transparent aperture 1144 andoptically-non-transparent stop region 1146. Aperture 1144 is configuredto define a narrow field of view when placed at the focal plane of animaging optic, such as bulk receiving optic 1060. As used herein, theterm “optically-transparent” refers to a material that allows most orall incident light to pass through. As used herein, the term “opticallynon-transparent” refers to a material that allows little to no light topass through, e.g., a reflecting or absorbing surface. The aperturelayer 1140 is configured to receive the input marginal ray lines 1133.The aperture layer 1140 may include an array of optically-transparentapertures and optically-non-transparent stop regions built upon a singlemonolithic piece such as an optically-transparent substrate. In someembodiments, aperture layer 1140 can be formed from a opticallynon-transparent material that forms stop regions 1146 and apertures 1144can be holes or openings in layer 1140.

In some embodiments, the receiver channel 1120 includes an optical lenslayer 1150 including a collimating lens 1151 characterized by a focallength. The collimating lens can be offset from the plane of aperture1144 and stop region 1146 by the focal length and aligned axially withaperture 1144 (i.e., the optical axis of the collimating lens is alignedwith the center of the aperture). In this manner the collimating lenscan be configured to collimate light rays passed by the aperture suchthat the light rays are travelling approximately parallel to the opticalaxis of collimating lens 1151. The optical lens layer 1150 mayoptionally include apertures, optically-non-transparent regions and tubestructures to reduce cross talk.

In some embodiments, the receiver channel 1132 includes an opticalfilter layer 1160 including an optical filter 1161, e.g., a Braggreflector type filter or the like. In some embodiments, the opticalfilter layer is disposed on a detector-side of the an optical lens layer1150 (as opposed to the aperture side). The optical filter layer isconfigured to pass normally incident photons at a specific operatingwavelength and passband. The optical filter layer 1160 may contain anynumber of optical filters 1161. The optical filter layer 1160 mayoptionally include apertures, optically-non-transparent regions and tubestructures to reduce cross talk.

In some embodiments, receiver channel 1132 includes a photosensor layer1170 including a pixel 1171 disposed behind the filter layer. The pixelcan be a photosensor capable of detecting photons with a detector activearea made of, e.g., a standard photodiode, an avalanche photodiode, anarray of SPADs, RCPs (Resonant Cavity Photo-diodes), or other suitablephotodetectors. Photosensor 1171 may be composed of several photondetector areas (e.g., each a different SPAD) cooperating together to actas a single pixel, often with higher dynamic range, faster responsetime, or other beneficial properties as compared to a single largephoton detection area. Photosensor layer 1170 refers to a layer made ofpixels and can include optional structures to improve detectionefficiency and reduce cross talk with neighboring receiver structures.Photosensor layer 1170 may optionally include diffusers, converginglenses, apertures, optically-non-transparent tube spacer structures,optically-non-transparent conical spacer structures, etc.

Stray light may be caused by roughness of optical surfaces,imperfections in transparent media, back reflections, and so on, and maybe generated at many features within the receiver channel 1132 orexternal to receiver channel 1132. The stray light can be directedthrough the filter region 1161 along a path non-parallel to the opticalaxis of collimating lens 1151; reflecting between the aperture 1144 andthe collimating lens 1151; and generally taking any other path ortrajectory possibly containing many reflections and refractions. Ifmultiple receiver channels are arrayed adjacent to one another, thisstray light in one receiver channel may be absorbed by a pixel inanother channel, thereby contaminating the timing, phase, or otherinformation inherent to photons. Accordingly, the receiver channel 1120may also feature several structures to reduce crosstalk and increasesignal between receiver channels. Examples of such structures and othersuitable receiver channels are described in U.S. patent application Ser.No. 15/979,295 entitled “Micro-optics for Imaging Module with MultipleConverging Lenses per Channel,” filed on May 14, 2018, the disclosure ofwhich is hereby incorporated by reference in its entirety for allpurposes.

3.Detector Array (e.g., SPADs)

FIGS. 12A and 12B show a top view of a SPAD-based photosensor arraylayer 1200 according to certain embodiments. Photosensor array layer1200 shown in FIG. 12A is a two-dimensional array of sensor channels1210 where each individual sensor channel can correspond, for example,to receiver channel 1055. Thus, each sensor channel 1210 can include agroup of SPADs as described above. In the example shown in FIG. 12A,photosensor array 1200 is an 18×4 array that includes a total of 72individual sensor channels 1210. Photosensor array 1200 also includes 8calibration pixels 1220 at the top of the array. Calibration pixels 1220can be, for example, covered by an opaque surface such that they are notexposed to any light and therefore can be used to measure dark counts.

FIG. 12B shows a magnified view of a subset of sensor channels 1210illustrating that each sensor channel 1210 can be formed from a group(array) of individual SPADs 1212 cooperating together to act as a singlepixel. Such an arrangement is advantageous when SPADs are used as thephotodetectors because after a photon detection event, a SPAD sufferssome deadtime during which external circuitry operates to quench theSPAD so that it is ready to detect again. Thus, a single SPAD has anupper limit to the light intensity (measured in photons/sec) that it candetect. That is, a single SPAD cannot detect a light intensity that isgreater than one photon per quench time. Collecting multiple SPADstogether as shown in FIG. 12B increases the overall intensity that canbe detected because not all SPADs will be saturated at the same time.Thus, a collection of N SPADs may be able to detect with N-times thedynamic range of a single SPAD.

4.Emitter Array (e.g., VCSELs)

FIGS. 13A and 13B depict simplified top and side views, respectively, ofan emitter array 1300 according to certain embodiments. The emitterarray 1300 can include a two-dimensional array of VCSEL emitters 1310that are fabricated on a single monolithic chip 1305 and whose patternmatches the photosensors pixels on a corresponding sensor chip. In thisexample, emitter array 1300 VC SEL array is 16×4 for a total of 64emitter channels 1310 to match the middle 64 detector channels shown inFIG. 12A above. Emitter array 1300 can also include a plurality of leads1320 over which signals to drive the various emitters in array 1300 canbe transmitted to the emitters.

As was described in reference to FIG. 12A, the monolithic VCSEL array ofoptical emitters can be arranged behind the TX-side micro-optics packageand behind the TX-side bulk optics module. Each VCSEL emitter can outputan illuminating beam of an initial diameter that is substantiallyidentical to (or slightly greater than) the diameter of a correspondingaperture defined either by the aperture layer or the numerical apertureof the micro-lenses of the micro-optics layer to ensure that all orsubstantially all of the light emitted by the VCSEL will be transmittedto objects in the field.

5. Bulk Optics

In some embodiments, the present disclosure provides a telecentric lightranging device having a fast lens system (e.g., f-number=1.0, 1.2, or1.4) and/or a lens system that is passively athermal over a specifiedtemperature range that is likely to be encountered when the lightranging device is used for obstacle detection and avoidance inautonomous navigation for automobiles, trucks or other vehicles. Inaddition, the bulk optical system possesses a low focal plane distortionand one or more of the optical elements may be AR coated to maximizeoptical throughput and reduce stray reflections, ghosting, andcross-talk amongst different sensor channels. Advantageously, theoptical system is image-space telecentric and thus provides a “straighton” view (when viewed from the object side) of each of the detectorchannels of the sensor array (each chief ray arrives perpendicular tothe focal plane), even those on the outer edges of the array.

As used herein, passively athermal describes an optics system, whereinthe spot quality of light from an extended source with non-zero angularsize focused by a lens system on an array does not change significantlyas temperature changes. If the back focal length of the lens systemchanges, and the array remains in the same place relative to the rearlens element, then the spot quality of light on the array would change.As used herein, spot quality can be defined by a fraction of light froman extended source with angular size of 0.13 degrees that is focusedonto the image plane and contained by a circle 25 μm in diameter. Anopto-mechanical system is considered to be passively athermal over atemperature range if the spot quality remains above 50% for alltemperatures in the temperature range. The diameters and angular sizeslisted are exemplary and depend on the size of the apertures in themicro-optic array, the focal length of the system, etc.

FIG. 14 depicts a simplified schematic of a portion of an optical module1400 that provides a thermally stable image plane over a wide range oftemperatures according to some embodiments. Optical module 1400 includesan array 1410, a bulk lens system 1420, a lens housing 1430, and a mount1440 to mechanically couple the housing with the array. Optical module1400 can be representative of an embodiment of light sensing module 330(in which case array 1410 can be an array of photosensors) or anembodiment of light emitting module 340 (in which case array 1410 can bean array of emitters), and in some embodiments mount 1440 canrepresentative of a portion of mount 905 shown in FIG. 9. A lightranging device according to some embodiments of the disclosure caninclude a first optical module 1400 as a light sensing module and asecond module 1400 as a light emitting module.

Array 1410 can be planar (e.g., having irregularity from a perfect planeless than 1 mm peak-to-valley over a 10 mm diameter disc) for ease inmanufacturing (e.g., forming arrays in bulk on a semiconductorsubstrate, wherein there are a plurality of emitters or detectors in onearray). In some embodiments, array 1410 can include a micro-opticsstructure, such as transmitter micro-optics package 1020 or receivermicro-optics package 1050 discussed above with respect to FIG. 10depending on optical module 1400 is implemented as a light sensingmodule or as a light emitting module.

As shown in FIG. 14, lens system 1420 can include a first lens 1422, asecond lens 1424, a third lens 1426, and a fourth lens 1428. In someembodiments, the first lens, the second lens, the third lens, and thefourth lens are mounted in the lens housing 1430. When implemented aspart of an imager sensor (i.e., array 1410 is an array of photosensors),lens housing 1430, lens system 1420, and mount 1440 are configured topassively focus light from the lens system to the photosensor array overa temperature range (e.g., from −40 Celsius to 85 Celsius, −50 Celsiusto 95 Celsius, −35 Celsius to 60 Celsius, −40 Celsius to 105 Celsius,−45 Celsius to 110 Celsius, or −35 Celsius to 100 Celsius). Inembodiments that include a micro-optics structure in the array, the lenssystem 1420 is configured to passively focus light from the lens systemto the aperture layer of the micro-optics structure and the variousmicro-optic components in the micro-optic structure can then focus lightreceived at each individual micro-optic channel to the correspondingphotosensor for that channel.

The array can be kept at the image plane of the lens system for varyingtemperatures. Materials can be chosen to reduce cost, reduce weight,and/or maintain the image plane at the array. To reduce costs, firstlens 1422, second lens 1424, the forth lens 1428 can be made of plastic(e.g., OKP-1), while third lens 1426 can be made of glass (e.g., toreduce temperature variations in the lens system). A nominal distancebetween an apex of the fourth lens and the image plane is 8 mm. In thelens assembly shown, the image plane moves toward the fourth lens astemperature increases. This is perhaps counter intuitive given that theindex of refraction for plastic decreases as temperature increases,which would usually push the image plane away from a plastic lens sincea lens with a lower refractive index would refract light less sharply(i.e., longer focal length) than a convex plastic lens of similar shapewith a higher refractive index (e.g., according to the Lensmaker'sEquation where focal length is inversely proportional to a differencebetween the refractive index of the lens and air, where refractive indexof air equals 1; see also Snell's Law). The combination of a glass lenswith two or more plastic lenses may allow the effective focal length ofthe lens system to decrease with increase of temperature even though oneor more plastic lenses in the lens system has a focal length thatincreases with temperature.

Lens housing 1430 (e.g., made of polycarbonate) can elongate astemperature increases. In some embodiments, mount 1440 attaches to lenshousing 1430 near third lens 1426, so that fourth lens 1428 moves to theright as temperature of the housing increases. Material of mount 1440,which separates lens housing 1430 from array 1410, expands withincreasing temperature, moving lens housing 1430 away (e.g., left) fromarray 1410. Simultaneously, lens housing 1430 expands with increasingtemperature moving the fourth lens 1428 toward (e.g., right) array 1410.Also simultaneously, the back focal shift moves the image planeleftward, as described above. By choosing the housing material CTE,mount material CTE, and the housing-to-mount interface locationappropriately, the back focal shift can be compensated by theaforementioned housing expansion and mount expansion such that the imageplane remains approximately coincident with the array over thetemperature range.

In some embodiments, mount 1440 can be coupled with lens housing 1430near the glass lens (i.e., third lens 1426 in some embodiments). In someembodiments, mount 1440 can be coupled with lens housing 1430 near theglass lens so that a lens of lens system 1410 nearest array 1410 (e.g.,fourth lens 1428) can move in relation to array 1410 (e.g., toward thearray) as the focal length of lens system 1420 moves in relation toarray 1410 (e.g., away from the array). In some embodiments, near can bea point or line on the outside of lens housing 1430, nearest the glasslens, and/or or within +/−5 mm or +/−10 mm from the point or line.

The spot quality of the lens system in FIG. 14 was experimentallyverified for a temperature range from −5 degrees C. to 70 degrees C.using the Zemax optical design program. In some embodiments, the insideof the LIDAR unit can be deliberately heated when the environment getsbelow a specific temperature. For example, when the environment is −40degrees C., internal components of the LIDAR unit can be heated to keepthe lens system at a temperature of −5 degrees C. or higher. In someembodiments a light ranging device can include a temperature sensor anda heating element (e.g., a resistive heater) that can heat the lenssystem when the temperature drops below a predetermined level asdetected by the temperature sensor. Accordingly, system 1400 can beexpected to perform well from at least temperatures ranging from −40degrees C. to 70 degrees C. (a temperature range of 100 degrees). Invarious embodiments, system 1400 can provide a stable image plane overtemperature ranging from 0 degrees C. to 32 degrees C.; from 0 degreesC. to 55 degrees C.; from −10 degrees C. to 32 degrees C.; from −10degrees C. to 55 degrees C.; from −20 degrees C. to 60 degrees C.; from−40 degrees C. to 85 degrees C.; and combinations thereof In someembodiments, the temperature range can be from −40 degrees C. to 105degrees C. (a temperature range of 145 degrees).

It can be often desirable to make lens housing 1430 out of material witha comparable coefficient of thermal expansion (CTE) to the lenses toavoid stressing the lenses. Changing the housing material can alsochange how the lens elements are spread apart as temperature increases.In some embodiments, the material CTE of lens housing 1430 is notchanged/tuned substantially to prevent reduction in optical performance.Thus, the lens housing material has a CTE close to that of the lenses;and not all possible materials for the housing are considered becausesome housing materials have CTEs that are sufficiently different fromCTEs of lenses that stress in the lenses will occur, which can result indegradation of optical performance of the lenses.

The CTE of lens housing 1430 can be matched, over a temperature range,with lens system 1420 so that a focal plane of lens system 1420 isstable relative to lens housing 1430 over the temperature range. In someembodiments, a thermal coefficient of mount 1440 is matched with lenssystem 1420 and/or with thermal expansion of lens housing 1430 so thatthe focal plane is stable relative to a position of the detector (e.g.,detector array) over the temperature range. As used herein, a focalplane is said to be “stable” over a range of temperatures if the focalplane maintains a predetermined resolution at the detector for thesystem over the given temperature range. As an example, in someembodiments a predetermined resolution requires light focused to a pointat the detector to have 50% of the light in a 25 micron circle, in otherembodiments a predetermined resolution requires light focused to a pointat the detector to have 80% of the light in a 20 micron circle. The CTEof the material of mount 1440 can be chosen with a caveat that materialof mount 1440 is strong and/or mechanically rigid (lower CTE materialstend to be stronger). In this example, the fact that the back focalshift is negative (leftward) rather than positive (rightward) allows avery rigid glass filled polymer, or even a metal like magnesium oraluminum, to be used for the separating material of mount 1440.

FIGS. 15A, 15B, and 15C depict an optical module 1500 according to someembodiments of the disclosure. Optical module 1500 includes a lenssystem 1520 with four lenses (of which only two, lenses 1522 and 1528,are visible in FIGS. 15A-15C) and a housing 1530. Lens system 1520 canbe, for example, lens system 1420, while housing 1530 can be, forexample, lens housing 1430. Since image sensors are generally notcircular, the lenses of assembly system 1500 generally do not need to becircular. For example, a photosensor array associated with lens assembly1500 can be narrow and tall, so lenses can be clipped in a rectangularfashion. It is typically easier and less expensive to make rectangularmolded polymer optics, while it can be more expensive to grind glasslenses into rectangular shapes. The diameter of the third lens (notshown in FIGS. 15A-15C) can define a minimum width of the lens system,thereby defining part of the rectangular shape. By using a circularglass element and rectangular molded polymer optics lens assembly 1500can be relatively easy and cheap to manufacture.

In some embodiments, two housings are put as close together as possible(e.g., touching), which is another reason to keep the glass lens (e.g.,lens 3) small. For example, the light ranging device can include a firstlens system mounted in a first housing, a second lens system mounted ina second housing, a sensor array, and an emitter array. The first lenssystem, the first housing, and the sensor array can form a first unit.The second lens system, the second housing, and the emitter array canform a second unit. The first unit and the second unit can be placedside by side as close as possible (e.g., no more than 2.5 cm spacedapart in some embodiments and no more than 5.0 cm in other embodiments)so that light emitted from the second unit and reflected/scattered isgathered by the first unit in similar field of views as the second lenssystem projected light from the emitter array.

Lens system 1520 can be designed to be a fast lens system. In someembodiments, the f-number of lens system 1520 is between 1.0 and 2.4(e.g., 1.2). The spot sizes on the sensor array can have 80% of thelight in a 20 μm circle. Further, lens system 1520 can have a tracklength equal to or less than 100 mm, 50 mm, 35 mm, and/or 20 mm, and/orequal to or greater than 5, 10, 15, 20, and/or 25 mm.

In various instances, bulk lens systems according to the presentdisclosure can include: two or more plastic lenses and at least oneglass lens; two or more plastic lenses; and/or one or more glass lenses.In some embodiments, micro-optic structure can be included as part ofthe array as described above. The micro-optics can modify lightdifferently for different emitters and/or detectors on the array,whereas the bulk lens system modifies light for the entire array. Insome embodiments there is one or more micro-optic elements for eachindividual array element.

FIG. 16A depicts a top view of an embodiment of an optical module 1600that can be, for example, optical module 1500. Cross section A-A isidentified in FIG. 16A. FIG. 16B depicts an embodiment of cross sectionA-A. As shown in FIG. 16B, optical module 1600 includes four opticalelements, including: element 1622 (e.g., lens 1), element 1624 (e.g.,lens 2), element 1626 (e.g., lens 3), and element 1628 (e.g., lens 4);and a housing 1630. FIG. 16C shows a magnified portion of the crosssection A-A. The magnified portion shows one example of how lens 1624and lens 1626 can be mounted in housing 1630. The aperture stop 1625 oflens system 1600 is between lens 1624 and lens 1626. The aperture stop1625 can be used to secure lens 1624 within the housing.

FIG. 16D depicts a side view of an embodiment of lens assembly 1600.Cross section B-B is identified in FIG. 16D. FIG. 16E depicts anembodiment of cross section B-B. Lens 1, lens 2, lens 3, lens 4, and thehousing are shown.

FIG. 17A, depicts a cross section of an embodiment of first lens (lens1522). The first lens has a first surface S1 and a second surface S2.The first surface S1 of lens 1522 and the second surface S2 of lens 1are spherical. The first surface S1 of the first lens can be a convexsurface. The second surface S2 of the first lens can be a concavesurface. Light traveling from left to right can be focused by the firstlens. The first surface of the first lens can be larger than the secondsurface of the first lens to gather light (e.g., reduce the f-number oflens system) for the lens system.

FIG. 17B, depicts a cross section of an embodiment of the second lens(lens 1524). The second lens has a first surface S1 and a second surfaceS2. The first surface S1 of lens 1524 and the second surface S2 of lens2 are aspherical. The first surface S1 of the second lens can be aconvex surface. The second surface S2 of the second lens can be planar,slightly convex, or slightly concave. Light traveling from left to rightcan be defocused by the second lens.

FIG. 17C, depicts a cross section of an embodiment of the third lens(lens 1526). The third lens has a first surface S1 and a second surfaceS2. The first surface S1 of lens 1526 and the second surface S2 of lens3 are spherical. As examples, the third lens can have a width (e.g.,diameter) equal to or greater than 10 mm and equal to or less than 20 mm(e.g., 11, 11.5, 12, 12.5, 13, 13.5, 14, and/or 14.5 mm). In someembodiments, the third lens is a high-index glass. In some embodiments,an index of the glass does not change (e.g., change equal to or lessthan 0.05%) for the temperature range of 100 degrees. The first surfaceS1 of the third lens can be planar, slightly convex, or slightlyconcave. The second surface S2 of the third lens can be convex. Lighttraveling from left to right can be collimated or slightly focused bythe third lens.

FIG. 17D, depicts a cross section of an embodiment of the fourth lens(lens 1528). The fourth lens has a first surface S1 and a second surfaceS2. The first surface S1 of lens 4 and the second surface S2 of lens 4are aspherical. The first surface S1 of the fourth lens can be convex.The second surface S2 of the third lens can be convex. Light travelingfrom left to right can be focused to the array.

By mixing plastic and glass lenses, as well as mixing aspherical andspherical lenses, an economical, light, compact, and/or athermal lightranging device can be made for autonomous vehicles.

In some embodiments, the lens system has a fixed focal length (e.g.,fixed focal length while at constant temperature; not a zoom lens). Insome embodiments, the lens system has a fixed focal length to reducesize, weight, number of parts, and/or complexity of the lens system.

FIG. 18 depicts an embodiment of an optical module 1800 with threelenses: a first lens 1822; a second lens 1824; and a third lens 1826.The first lens, the second lens, and the third lens are mounted in ahousing 1830. A connecter 1805 couples the housing with a sensor 1810(e.g., a sensor in an array). The first lens, the second lens, and thethird lens can be made of plastic (e.g., OKP-1). The first lens, thesecond lens, and the third lens are part of a lens system 1810. Lenssystem 1810 is estimated to have a focal shift of around 105 μm over a50 degree C. temperature range (e.g., from 0 to 50 degrees C.). Housing1830 can be made of a high CTE material, and/or the mount 1840 attachesnear lens 1822, to hold the focal plane of lens system 1810 at thearray. In the embodiment in FIG. 18, polycarbonate (CTE=70 ppm/C) isused and mount 1840 is attached to housing 1830 25-35 mm away from thearray. A combination of mount 1840 attached to the housing 30 mm awayfrom array 1810, a movement of lenses of the lens system 1810 due tothermal expansion of housing 1830, a movement of housing 1830 due tothermal expansion of mount 1840, and/or a focal shift of lens system1810 due to temperature change are matched to align the focal plane ofthe lens system with the array.

The above description of exemplary embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdescribed, and many modifications and variations are possible in lightof the teaching above. The embodiments were chosen and described inorder to explain the principles of the invention and its practicalapplications to thereby enable others skilled in the art to utilize theinvention in various embodiments and with various modifications as aresuited to the particular use contemplated.

As an example, while various embodiments and examples described abovehave focused primarily on the application of light ranging within thecontext of 3D sensing for automotive or other road vehicle use cases,systems disclosed herein can be used in any application withoutdeparting from the scope of the present disclosure. The small, or evenminiature, form factor of a LIDAR system according to the presentdisclosure enables a number of additional use cases, e.g., forsolid-state light ranging systems. As specific examples, systems can beused in 3D cameras and/or depth sensors within devices, such as mobilephones, tablet PCs, laptops, desktop PCs, or within other peripheralsand/or user-interface devices. As other examples, one or moreembodiments could be employed within a mobile device to support facialrecognition and facial tracking capabilities, eye tracking capabilities,and/or for 3D scanning of objects. Other use cases includeforward-facing depth cameras for augmented and virtual realityapplications in mobile devices.

Other applications include deployment of one or more systems on airbornevehicles, such as airplanes, helicopters, drones, and the like. Suchexamples could provide 3D sensing and depth imaging to assist withnavigation (autonomous or otherwise) and/or to generate 3D maps forlater analysis, e.g., to support geophysical, architectural, and/orarcheological analyses. Systems can also be mounted to stationaryobjects and structures, such as buildings, walls, poles, bridges,scaffolding, and the like. In such cases, the systems can be used tomonitor outdoor areas, such as manufacturing facilities, assembly lines,industrial facilities, construction sites, excavation sites, roadways,railways, bridges, etc. Furthermore, systems can be mounted indoors andused to monitor movement of persons and or objects within a building,such as the movement of inventory within a warehouse or the movement ofpeople, luggage, or goods within an office building, airport, trainstation, etc.

As another example, while various examples above included lasers in theIR or near-IR wavelengths as the emitters in LIDAR systems according tosome embodiments of the disclosure, embodiments of the disclosure arenot limited to any particular wavelength of light or other types ofradiation for the emitters. For example, in some embodiments, theemitters can be lasers that generate pulses having any suitable knownoperating wavelength including a green (532 nm) wavelength, which can beparticularly well-suited for underwater applications, or UV wavelengthsthat can be particularly useful for atmospheric LIDAR systems. As wouldbe appreciated by one of ordinary skill in the art with the benefit ofthis disclosure, many different applications of light ranging systemsare possible and, as such, the examples provided herein are provided forillustrative purposes only and shall not be construed to limit the usesof such systems to only the examples explicitly disclosed.

The specific details of particular embodiments described above may becombined in any suitable manner without departing from the spirit andscope of embodiments of the invention. However, other embodiments of theinvention may be directed to specific embodiments relating to eachindividual aspect, or specific combinations of these individual aspects.For example, to reduce a spot size on the array, more than four lensescould be used, using more aspheric surfaces, and/or using multiple typesof plastics could be used. As another example, in some embodiments acurved detector and/or emitter can be used. Additionally, in someembodiments three lenses are used instead of four (e.g., two lensesplastic and one lens glass). These examples and others are includedwithin the scope of the present disclosure.

What is claimed is:
 1. A light ranging system comprising: a shaft; afirst circuit board assembly that includes a stator assembly comprisinga plurality of stator elements arranged about the shaft on a surface ofthe first circuit board assembly; a second circuit board assemblyrotationally coupled to the shaft, wherein the second circuit boardassembly includes a rotor assembly comprising a plurality of rotorelements arranged about the shaft on a surface of the second circuitboard assembly such that the plurality of rotor elements are alignedwith and spaced apart from the plurality of stator elements; a lightranging device coupled to rotate with the second circuit board assembly,the light ranging device including a light source configured to transmitlight pulses to objects in a surrounding environment, and detectorcircuitry configured to detect reflected portions of the light pulsesthat are reflected from the objects in the surrounding environment andto compute ranging data based on the reflected portion of the lightpulses; and a stator driver circuit disposed on either the second or thefirst circuit board assemblies and configured to provide a drive signalto the plurality of stator elements, thereby imparting anelectromagnetic force on the plurality of rotor elements to drive arotation of the second circuit board assembly about the shaft.
 2. Thelight ranging system of claim 1 wherein the plurality of rotor elementsand the plurality of stator elements are arranged symmetrically aboutthe shaft.
 3. The light ranging system of claim 1 wherein the secondcircuit board assembly further includes a plurality of optical uplinkreceivers disposed on a circuit board of the second circuit boardassembly and symmetrically arranged about the shaft.
 4. The lightranging system of claim 3 wherein the plurality of rotor elements arefarther from the shaft than plurality of optical uplink receivers. 5.The light ranging system of claim 1 wherein the first circuit boardassembly further includes a plurality of optical uplink transmittersdisposed on a circuit board of the first circuit board assembly andsymmetrically arranged about the shaft.
 6. The light ranging system ofclaim 5 wherein a distance between the shaft and each of the pluralityof stator elements is greater than a distance between the shaft and eachof a plurality of optical uplink transmitters.
 7. The light rangingsystem of claim 1 wherein the plurality of stator elements includes aplurality of solenoid coils, each of the plurality of solenoid coilsbeing arranged in a ring around the shaft.
 8. The light ranging systemof claim 7 wherein each of the plurality of stator elements has alongitudinal axis perpendicular to the first circuit board assembly andcomprises a solenoid coil wrapped around a core of magnetic material,wherein each rotor element in the plurality of rotor elements comprisesa magnet having its poles arranged opposite the poles of the magnetsadjacent to the rotor element.
 9. The light ranging system of claim 8wherein a number of stator elements in the plurality of stator elementsis a multiple of three and the light ranging system further comprises amotor driver circuit coupled to the plurality of stator elements andconfigured to provide a 3-phase alternating signal to the plurality ofstator elements.
 10. The light ranging system of claim 8 wherein theplurality of rotor elements includes a plurality of permanent magnets.11. The light ranging system of claim 1 wherein the plurality of statorelements includes a plurality of permanent magnets arranged in a ringaround the shaft, and the plurality of rotor elements comprises aplurality of solenoid coils arranged in a ring around the shaft directlyopposite the plurality of permanent magnets.
 12. The light rangingsystem of claim 11 wherein the plurality of stator elements includes atleast 12 stator elements.
 13. The light ranging system of claim 1wherein the second circuit board assembly further includes an opticaldownlink transmitter configured to transmit ranging data from the lightranging device through a central hole within the shaft, and wherein thefirst circuit board assembly further includes an optical downlinkreceiver configured to receive ranging data from the optical downlinktransmitter via the central hole within the shaft.
 14. The light rangingsystem of claim 1 wherein the first circuit board assembly comprises awireless power transmission subsystem configured to transmit power tothe light ranging device that is electrically connected to the secondcircuit board assembly, the wireless power transmission subsystemcomprising a transmitter coil disposed on the first circuit boardassembly and disposed around the shaft, wherein the second circuit boardassembly comprises a wireless power receiver subsystem configured toreceive power from the wireless power transmission subsystem, thewireless power receiver subsystem comprising a receiver coil that isdisposed on the second circuit board assembly and disposed around theshaft.
 15. A light ranging system comprising: a stationary enclosurehaving an optically transparent window and a base; a hollow shaftdisposed within the enclosure; a bearing system coupled to the hollowshaft; a first circuit board assembly disposed within the enclosure andparallel with a first plane perpendicular to the hollow shaft, the firstcircuit board assembly including a stator assembly comprising aplurality of evenly spaced stator elements arranged annularly about theshaft on a surface of the first circuit board assembly; a second circuitboard assembly disposed within the enclosure parallel to the first planeand rotationally coupled to the shaft by the bearing system, wherein thesecond circuit board assembly includes a rotor assembly comprising aplurality of evenly spaced rotor elements arranged annularly about theshaft on a surface of the second circuit board assembly such that theplurality of rotor elements are aligned with and spaced apart from theplurality of stator elements; a light ranging device coupled to rotatewith the second circuit board assembly within the stationary enclosure,the light ranging device including a light source configured to transmitlight pulses through the window to objects in a surrounding environment,and detector circuitry configured to detect reflected portions of thelight pulses received through the window that are reflected from theobjects in the surrounding environment and to compute ranging data basedon the reflected portion of the light pulses; and a stator drivercircuit disposed on either the second or the first circuit boardassemblies and configured to provide a drive signal to the plurality ofstator elements, thereby imparting an electromagnetic force on theplurality of rotor elements to drive a rotation of the second circuitboard assembly and the light ranging device about the shaft.
 16. Thelight ranging system of claim 15 further comprising: a first opticalcommunication channel configured to optically transmit data between thefirst circuit board assembly and the second circuit board assemblythrough the hollow shaft, the first optical communication channelincluding a first optical component coupled to circuitry disposed on thefirst circuit board assembly and a second optical component coupled tocircuitry disposed in the second circuit board assembly; and a second,annular optical communication channel surrounding the hollow shaft andconfigured to optically transmit data between the first circuit boardassembly and the second circuit board assembly, the annular opticalcommunication channel including a first annular optical componentcoupled to circuitry disposed on the first circuit board assembly and asecond annular optical component coupled to circuitry disposed in thesecond circuit board assembly.
 17. The light ranging system of claim 16wherein the first optical communication channel is a downlink channelconfigured to transmit ranging data from the light ranging device to aprocessor coupled to the first circuit board subassembly and the secondoptical communication channel is an uplink channel configured totransmit control signals from the processor to the light ranging device.18. The light ranging system of claim 15 further comprising a heatspreading element coupled to the first circuit board assembly, whereincomponents of the light ranging system are configured to conduct heatfrom the second circuit board assembly to the base through the bearingsystem and the heat spreading element.
 19. The light ranging system ofclaim 15 wherein each of the plurality of evenly spaced stator elementshas a longitudinal axis perpendicular to the first circuit boardassembly and comprises a solenoid coil wrapped around a core of magneticmaterial, wherein each rotor element in the plurality of evenly spacedrotor elements comprises a magnet having its poles arranged opposite thepoles of the magnets adjacent to the rotor element.
 20. A light rangingsystem comprising: a shaft having a longitudinal axis; a first circuitboard assembly that includes a stator assembly comprising a plurality ofstator elements arranged about the shaft on a surface of the firstcircuit board assembly; a second circuit board assembly rotationallycoupled to the shaft and spaced apart from and in an opposingrelationship with the first circuit board assembly, wherein the secondcircuit board assembly includes a rotor assembly comprising a pluralityof rotor elements arranged about the shaft on a surface of the secondcircuit board assembly such that the plurality of rotor elements arealigned with and spaced apart from the plurality of stator elements; astator driver circuit disposed on either the second or the first circuitboard assemblies and configured to provide a drive signal to theplurality of stator elements, thereby imparting an electromagnetic forceon the plurality of rotor elements to drive a rotation of the secondcircuit board assembly about the longitudinal axis of the shaft; and alight ranging device mechanically coupled to the second circuit boardassembly such that the light ranging device rotates with the secondcircuit board assembly.